diff --git a/backend/apps/monitor/views.py b/backend/apps/monitor/views.py
index 4de3956..56d6134 100644
--- a/backend/apps/monitor/views.py
+++ b/backend/apps/monitor/views.py
@@ -994,19 +994,35 @@ def iam_user_project_policies_view(request, pk, pid):
         return Response({'error': 'not_found'}, status=status.HTTP_404_NOT_FOUND)
 
     new_policies = request.data.get('policies', [])
-    old_policies = project.attached_policies or []
 
     account, ak, sk = _get_volc_account(user.volc_account_id)
     if not ak:
         return Response({'error': 'no_credentials'}, status=status.HTTP_400_BAD_REQUEST)
 
     svc = IAMService(ak, sk)
+
+    # Get actual current policies from Volcengine (not local DB)
+    actual_old = []
+    try:
+        resp = svc.client.call('ListAttachedUserPolicies', {
+            'UserName': user.username,
+            'ProjectName': project.project_name,
+        })
+        for p in resp.get('Result', {}).get('AttachedPolicyMetadata', []):
+            scopes = p.get('PolicyScope', [])
+            for s in scopes:
+                if s.get('PolicyScopeType') == 'Project' and s.get('ProjectName') == project.project_name:
+                    actual_old.append(p.get('PolicyName', ''))
+                    break
+    except Exception:
+        actual_old = project.attached_policies or []
+
     attached = []
     detached = []
     errors = []
 
     # Remove policies that were removed
-    to_remove = [p for p in old_policies if p not in new_policies]
+    to_remove = [p for p in actual_old if p not in new_policies]
     for policy_name in to_remove:
         try:
             svc.detach_policy_in_project(user.username, policy_name, project.project_name)
@@ -1015,7 +1031,7 @@ def iam_user_project_policies_view(request, pk, pid):
             errors.append(f"移除 {policy_name}: {e}")
 
     # Add policies that are new
-    to_add = [p for p in new_policies if p not in old_policies]
+    to_add = [p for p in new_policies if p not in actual_old]
     for policy_name in to_add:
         try:
             svc.attach_policy_in_project(user.username, policy_name, project.project_name)