diff --git a/backend/app/api/v1/notifications.py b/backend/app/api/v1/notifications.py
index 8343bef..96499a6 100644
--- a/backend/app/api/v1/notifications.py
+++ b/backend/app/api/v1/notifications.py
@@ -82,6 +82,33 @@ async def get_unread_count(
         return success_response(data={"unread_count": 0})
 
 
+@router.get("/unread-by-project", response_model=dict)
+async def get_unread_by_project(
+    current_user: User = Depends(get_current_user),
+):
+    """按项目统计未读通知数量（与消息通知一致），返回 {project_id: count}"""
+    try:
+        counts = await notification_service.get_unread_count_by_project(current_user.id)
+        return success_response(data={"unread_by_project": counts})
+    except Exception as e:
+        print(f"Error fetching unread by project: {e}")
+        return success_response(data={"unread_by_project": {}})
+
+
+@router.put("/read-project/{project_id}", response_model=dict)
+async def mark_project_read(
+    project_id: int,
+    current_user: User = Depends(get_current_user),
+):
+    """将指定项目的所有未读通知标记为已读（打开项目时调用）"""
+    try:
+        count = await notification_service.mark_project_read(current_user.id, project_id)
+        return success_response(data={"marked": count}, message="项目通知已标记为已读")
+    except Exception as e:
+        print(f"Error marking project read: {e}")
+        return success_response(message="操作完成")
+
+
 @router.put("/{notification_id}/read", response_model=dict)
 async def mark_as_read(
     notification_id: str,
diff --git a/backend/app/api/v1/projects.py b/backend/app/api/v1/projects.py
index 3fb5c38..c48f453 100644
--- a/backend/app/api/v1/projects.py
+++ b/backend/app/api/v1/projects.py
@@ -54,6 +54,40 @@ def get_document_count(storage_key: str) -> int:
         return 0
 
 
+def get_project_document_stats(storage_key: str):
+    """
+    计算项目文档统计信息：返回 (doc_count, last_activity_at)
+    last_activity 取项目内 .md/.pdf 文档的最新文件修改时间（排除 _assets），
+    反映文档被编辑、导入、Git 拉取等真实活动时间，无需额外数据库字段。
+    """
+    from datetime import datetime
+    try:
+        project_path = storage_service.get_secure_path(storage_key)
+        if not project_path.exists():
+            return 0, None
+        assets_dir = project_path / "_assets"
+        count = 0
+        last_ts = None
+        for p in project_path.rglob("*"):
+            if not p.is_file():
+                continue
+            if p.suffix.lower() not in (".md", ".pdf"):
+                continue
+            if assets_dir in p.parents:
+                continue
+            count += 1
+            try:
+                ts = p.stat().st_mtime
+            except OSError:
+                continue
+            if last_ts is None or ts > last_ts:
+                last_ts = ts
+        last_activity = datetime.fromtimestamp(last_ts).isoformat() if last_ts else None
+        return count, last_activity
+    except Exception:
+        return 0, None
+
+
 async def attach_member_counts(db: AsyncSession, projects) -> dict:
     """批量查询项目的参与人数量（含所有者），返回 {project_id: count}"""
     if not projects:
@@ -96,7 +130,9 @@ async def get_my_projects(
     projects_data = []
     for p in all_projects:
         p_dict = ProjectResponse.from_orm(p).dict()
-        p_dict['doc_count'] = get_document_count(p.storage_key)
+        doc_count, last_activity_at = get_project_document_stats(p.storage_key)
+        p_dict['doc_count'] = doc_count
+        p_dict['last_activity_at'] = last_activity_at
         p_dict['member_count'] = member_counts.get(p.id, 0)
         projects_data.append(p_dict)
 
@@ -117,7 +153,9 @@ async def get_owned_projects(
     projects_data = []
     for p in projects:
         p_dict = ProjectResponse.from_orm(p).dict()
-        p_dict['doc_count'] = get_document_count(p.storage_key)
+        doc_count, last_activity_at = get_project_document_stats(p.storage_key)
+        p_dict['doc_count'] = doc_count
+        p_dict['last_activity_at'] = last_activity_at
         p_dict['member_count'] = member_counts.get(p.id, 0)
         projects_data.append(p_dict)
     return success_response(data=projects_data)
@@ -150,7 +188,9 @@ async def get_shared_projects(
         project_dict['owner_name'] = owner.username
         project_dict['owner_nickname'] = owner.nickname
         project_dict['user_role'] = member.role  # 添加用户角色
-        project_dict['doc_count'] = get_document_count(project.storage_key)
+        doc_count, last_activity_at = get_project_document_stats(project.storage_key)
+        project_dict['doc_count'] = doc_count
+        project_dict['last_activity_at'] = last_activity_at
         project_dict['member_count'] = member_counts.get(project.id, 0)
         projects_data.append(project_dict)
 
diff --git a/backend/app/services/notification_service.py b/backend/app/services/notification_service.py
index 87e3773..b020a4b 100644
--- a/backend/app/services/notification_service.py
+++ b/backend/app/services/notification_service.py
@@ -1,5 +1,6 @@
 import logging
 import json
+import re
 import time
 import uuid
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -20,6 +21,24 @@ class NotificationService:
     def _get_content_key(self, user_id: int) -> str:
         return f"notifications:content:{user_id}"
 
+    @staticmethod
+    def _extract_project_id_from_link(link: Optional[str]) -> Optional[int]:
+        """从通知链接中解析项目ID（兼容旧通知没有 project_id 字段的情况）"""
+        if not link:
+            return None
+        match = re.search(r"/projects/(\d+)", link)
+        return int(match.group(1)) if match else None
+
+    def _get_project_id(self, data: Dict[str, Any]) -> Optional[int]:
+        """从通知数据中获取项目ID"""
+        pid = data.get("project_id")
+        if pid is not None:
+            try:
+                return int(pid)
+            except (TypeError, ValueError):
+                pass
+        return self._extract_project_id_from_link(data.get("link"))
+
     async def create_notification(
         self,
         db: AsyncSession,
@@ -28,7 +47,8 @@ class NotificationService:
         content: str = None,
         type: str = "info",
         category: str = "system",
-        link: str = None
+        link: str = None,
+        project_id: Optional[int] = None
     ) -> Dict[str, Any]:
         """创建单条通知 (写入 Redis)"""
         redis = get_redis()
@@ -49,6 +69,8 @@ class NotificationService:
             "is_read": False,
             "created_at": timestamp
         }
+        if project_id is not None:
+            notification_data["project_id"] = project_id
         
         json_data = json.dumps(notification_data, ensure_ascii=False)
         order_key = self._get_order_key(user_id)
@@ -71,7 +93,9 @@ class NotificationService:
         title: str,
         content: str,
         user_ids: List[int],
-        link: str = None
+        link: str = None,
+        project_id: Optional[int] = None,
+        category: str = "system"
     ):
         """向指定多个用户发送系统通知"""
         redis = get_redis()
@@ -89,11 +113,13 @@ class NotificationService:
                     "title": title,
                     "content": content,
                     "type": "info",
-                    "category": "system",
+                    "category": category,
                     "link": link,
                     "is_read": False,
                     "created_at": timestamp
                 }
+                if project_id is not None:
+                    notification_data["project_id"] = project_id
                 json_data = json.dumps(notification_data, ensure_ascii=False)
                 
                 order_key = self._get_order_key(uid)
@@ -130,7 +156,9 @@ class NotificationService:
                 title=title, 
                 content=content, 
                 user_ids=member_ids, 
-                link=link
+                link=link,
+                project_id=project_id,
+                category=category
             )
 
     async def get_user_notifications(
@@ -224,6 +252,59 @@ class NotificationService:
             except:
                 pass
 
+    async def get_unread_count_by_project(self, user_id: int) -> Dict[int, int]:
+        """按项目统计未读通知数量（仅项目类通知），返回 {project_id: count}"""
+        redis = get_redis()
+        if not redis:
+            return {}
+
+        content_key = self._get_content_key(user_id)
+        all_jsons = await redis.hvals(content_key)
+        result: Dict[int, int] = {}
+        for js in all_jsons:
+            if not js:
+                continue
+            try:
+                data = json.loads(js)
+            except Exception:
+                continue
+            if data.get("is_read"):
+                continue
+            # 关联到项目的未读通知即计入该项目（兼容旧数据 category=system）
+            pid = self._get_project_id(data)
+            if pid:
+                result[pid] = result.get(pid, 0) + 1
+        return result
+
+    async def mark_project_read(self, user_id: int, project_id: int) -> int:
+        """将指定项目的未读通知全部标记为已读，返回标记数量"""
+        redis = get_redis()
+        if not redis:
+            return 0
+
+        content_key = self._get_content_key(user_id)
+        all_jsons = await redis.hvals(content_key)
+        updates = {}
+        count = 0
+        for js in all_jsons:
+            if not js:
+                continue
+            try:
+                data = json.loads(js)
+            except Exception:
+                continue
+            if data.get("is_read"):
+                continue
+            # 关联到该项目的未读通知全部标记已读（兼容旧数据 category=system）
+            if self._get_project_id(data) == project_id:
+                data["is_read"] = True
+                updates[data.get("id")] = json.dumps(data, ensure_ascii=False)
+                count += 1
+
+        if updates:
+            await redis.hset(content_key, mapping=updates)
+        return count
+
     async def mark_all_read(self, user_id: int):
         """标记所有已读"""
         redis = get_redis()
diff --git a/frontend/src/api/notification.js b/frontend/src/api/notification.js
index 0a3a7bf..b4b50c2 100644
--- a/frontend/src/api/notification.js
+++ b/frontend/src/api/notification.js
@@ -43,3 +43,23 @@ export function markAllAsRead() {
     method: 'put',
   })
 }
+
+/**
+ * 按项目统计未读通知数量（与消息通知一致）
+ */
+export function getUnreadByProject() {
+  return request({
+    url: '/notifications/unread-by-project',
+    method: 'get',
+  })
+}
+
+/**
+ * 将指定项目的所有未读通知标记为已读（打开项目时调用）
+ */
+export function markProjectNotificationsRead(projectId) {
+  return request({
+    url: `/notifications/read-project/${projectId}`,
+    method: 'put',
+  })
+}
diff --git a/frontend/src/pages/Document/DocumentPage.jsx b/frontend/src/pages/Document/DocumentPage.jsx
index 2e18d5a..21fdb0b 100644
--- a/frontend/src/pages/Document/DocumentPage.jsx
+++ b/frontend/src/pages/Document/DocumentPage.jsx
@@ -15,6 +15,8 @@ import { getProjectTree, getFileContent, getDocumentUrl, getExportPdfUrl } from
 import { gitPull, gitPush, getGitRepos } from '@/api/project'
 import { getFileShareInfo, createOrUpdateFileShare, deleteFileShare } from '@/api/share'
 import { searchDocuments } from '@/api/search'
+import { markProjectNotificationsRead } from '@/api/notification'
+import useNotificationStore from '@/stores/notificationStore'
 import VirtualPDFViewer from '@/components/PDFViewer/VirtualPDFViewer'
 import FloatingToc from '@/components/FloatingToc/FloatingToc'
 import Toast from '@/components/Toast/Toast'
@@ -196,6 +198,14 @@ function DocumentPage() {
     loadFileTree()
   }, [projectId])
 
+  // 打开项目后，将该项目的未读更新通知标记为已读（与消息通知联动）
+  useEffect(() => {
+    if (!projectId) return
+    markProjectNotificationsRead(projectId)
+      .then(() => useNotificationStore.getState().fetchUnreadCount())
+      .catch(() => {})
+  }, [projectId])
+
   const handleClose = () => {
     Modal.confirm({
       title: '确认退出',
diff --git a/frontend/src/pages/ProjectList/ProjectList.css b/frontend/src/pages/ProjectList/ProjectList.css
index 0d04f33..c9612fb 100644
--- a/frontend/src/pages/ProjectList/ProjectList.css
+++ b/frontend/src/pages/ProjectList/ProjectList.css
@@ -64,6 +64,37 @@
   z-index: 1;
 }
 
+/* 参与项目右上角：未读更新通知数角标 */
+.project-card-update-badge {
+  position: absolute;
+  top: 12px;
+  right: 12px;
+  z-index: 2;
+  min-width: 20px;
+  height: 20px;
+  padding: 0 6px;
+  border-radius: 999px;
+  background: linear-gradient(135deg, #ff4d4f 0%, #f5222d 100%);
+  color: #fff;
+  font-size: 11px;
+  font-weight: 600;
+  line-height: 20px;
+  text-align: center;
+  box-shadow: 0 2px 6px rgba(245, 34, 45, 0.45);
+  animation: project-badge-pop 0.25s ease-out;
+}
+
+@keyframes project-badge-pop {
+  from {
+    transform: scale(0.6);
+    opacity: 0;
+  }
+  to {
+    transform: scale(1);
+    opacity: 1;
+  }
+}
+
 /* 卡片主体：标题在上、描述占中间弹性空间、元信息贴底 */
 .project-card-body {
   flex: 1;
@@ -249,20 +280,18 @@ body.dark .project-card-role-badge.role-editor {
   color: var(--text-color-secondary);
 }
 
-/* ========== 我的项目卡片：蓝色管理风 ========== */
+/* ========== 我的项目卡片：蓝色管理风（无顶边） ========== */
 .project-card-my {
   text-align: left;
-  border-top: 3px solid var(--link-color);
 }
 
 .project-card-my .ant-card-actions {
   background: var(--bg-color-secondary);
 }
 
-/* ========== 参与的项目卡片：绿色协作风 ========== */
+/* ========== 参与的项目卡片：绿色协作风（无顶边） ========== */
 .project-card-share {
   text-align: left;
-  border-top: 3px solid #52c41a;
 }
 
 .project-card-share .ant-card-actions {
diff --git a/frontend/src/pages/ProjectList/ProjectList.jsx b/frontend/src/pages/ProjectList/ProjectList.jsx
index 13ded7e..f2d6f08 100644
--- a/frontend/src/pages/ProjectList/ProjectList.jsx
+++ b/frontend/src/pages/ProjectList/ProjectList.jsx
@@ -6,6 +6,8 @@ import { getMyProjects, getOwnedProjects, getSharedProjects, createProject, dele
 import { getProjectShareInfo, updateProjectShareSettings } from '@/api/share'
 import { getUserList } from '@/api/users'
 import { searchDocuments } from '@/api/search'
+import { getUnreadByProject, markProjectNotificationsRead } from '@/api/notification'
+import useNotificationStore from '@/stores/notificationStore'
 import ListActionBar from '@/components/ListActionBar/ListActionBar'
 import Toast from '@/components/Toast/Toast'
 import useProjectKnowledge from './useProjectKnowledge'
@@ -39,6 +41,7 @@ function ProjectList({ type = 'my' }) {
   const navigate = useNavigate()
   const { user: currentUser } = useUserStore()
   const [currentPage, setCurrentPage] = useState(1)
+  const [unreadByProject, setUnreadByProject] = useState({})
   const pageSize = 8
 
   // 参与项目角色 -> 显示名称
@@ -59,6 +62,22 @@ function ProjectList({ type = 'my' }) {
     }
   }
 
+  // 相对时间（用于“最后更新”）
+  const formatRelativeTime = (dateStr) => {
+    if (!dateStr) return ''
+    const d = new Date(dateStr)
+    if (Number.isNaN(d.getTime())) return ''
+    const diff = Date.now() - d.getTime()
+    if (diff < 60 * 1000) return '刚刚'
+    const minutes = Math.floor(diff / (60 * 1000))
+    if (minutes < 60) return `${minutes} 分钟前`
+    const hours = Math.floor(minutes / 60)
+    if (hours < 24) return `${hours} 小时前`
+    const days = Math.floor(hours / 24)
+    if (days < 30) return `${days} 天前`
+    return formatDate(dateStr)
+  }
+
   // 卡片归属用户显示名（我的项目 -> 当前用户；参与项目 -> 项目所有者）
   const cardOwnerName = (project) => {
     if (type === 'my') {
@@ -166,6 +185,14 @@ function ProjectList({ type = 'my' }) {
         res = await getMyProjects()
       }
       setProjects(res.data || [])
+      // 参与项目：加载每个项目的未读更新通知数（与消息通知保持一致）
+      if (type === 'share') {
+        getUnreadByProject()
+          .then((unreadRes) => setUnreadByProject(unreadRes.data?.unread_by_project || {}))
+          .catch(() => setUnreadByProject({}))
+      } else {
+        setUnreadByProject({})
+      }
     } catch (error) {
       console.error('Fetch projects error:', error)
     } finally {
@@ -394,6 +421,20 @@ function ProjectList({ type = 'my' }) {
   }
 
   const handleOpenProject = (projectId) => {
+    // 打开参与项目时，将其未读更新通知标记为已读（与消息通知联动）
+    if (type === 'share' && unreadByProject[projectId]) {
+      markProjectNotificationsRead(projectId)
+        .then(() => {
+          setUnreadByProject((prev) => {
+            if (!prev[projectId]) return prev
+            const next = { ...prev }
+            delete next[projectId]
+            return next
+          })
+          useNotificationStore.getState().fetchUnreadCount()
+        })
+        .catch(() => {})
+    }
     navigate(`/projects/${projectId}/docs`)
   }
 
@@ -685,10 +726,19 @@ function ProjectList({ type = 'my' }) {
                     <Tooltip key="view" title="进入项目"><EyeOutlined /></Tooltip>,
                   ]}
                 >
-                  {/* 公开项目标识 */}
-                  {project.is_public === 1 && (
+                  {/* 公开项目标识（仅我的项目显示，参与项目不显示） */}
+                  {type === 'my' && project.is_public === 1 && (
                     <div className="project-card-public-badge">公开</div>
                   )}
+                  {/* 参与项目：右上角显示未读更新通知数（打开项目后已读） */}
+                  {type === 'share' && (unreadByProject[project.id] || 0) > 0 && (
+                    <div
+                      className="project-card-update-badge"
+                      title={`${unreadByProject[project.id]} 条项目更新通知`}
+                    >
+                      {unreadByProject[project.id] > 99 ? '99+' : unreadByProject[project.id]}
+                    </div>
+                  )}
 
                   {/* 统一的卡片骨架：标题 + 描述（主要信息）+ 底部统计/归属/角色 */}
                   <div className="project-card-body">
@@ -706,8 +756,8 @@ function ProjectList({ type = 'my' }) {
                           <span className="project-stat-item" title="文档数量">
                             <FileTextOutlined /> {project.doc_count || 0} 文档
                           </span>
-                          <span className="project-stat-item" title="创建时间">
-                            <CalendarOutlined /> {formatDate(project.created_at) || '—'}
+                          <span className="project-stat-item" title="最后更新时间">
+                            <CalendarOutlined /> {formatRelativeTime(project.last_activity_at) || formatDate(project.created_at) || '—'}
                           </span>
                           <span className="project-stat-item" title="项目参与人数量">
                             <TeamOutlined /> {project.member_count ?? 0} 人参与