diff --git a/domain/backup/api.py b/domain/backup/api.py
index 7f847b2..aab995c 100644
--- a/domain/backup/api.py
+++ b/domain/backup/api.py
@@ -28,7 +28,7 @@ async def export_backup(
     data = await BackupService.export_data(sections=sections)
     timestamp = datetime.datetime.now().strftime("%Y-%m-%d_%H-%M-%S")
     headers = {"Content-Disposition": f"attachment; filename=foxel_backup_{timestamp}.json"}
-    return JSONResponse(content=data.model_dump(), headers=headers)
+    return JSONResponse(content=data.model_dump(mode="json"), headers=headers)
 
 
 @router.post("/import", summary="导入数据")
diff --git a/domain/backup/service.py b/domain/backup/service.py
index f09d632..150b843 100644
--- a/domain/backup/service.py
+++ b/domain/backup/service.py
@@ -82,6 +82,9 @@ class BackupService:
         share_links = cls._serialize_datetime_fields(
             shares, ["created_at", "expires_at"]
         )
+        user_accounts = cls._serialize_datetime_fields(
+            users, ["created_at", "last_login"]
+        )
         ai_providers = cls._serialize_datetime_fields(
             providers, ["created_at", "updated_at"]
         )
@@ -99,7 +102,7 @@ class BackupService:
             version=VERSION,
             sections=sections,
             storage_adapters=list(adapters),
-            user_accounts=list(users),
+            user_accounts=user_accounts,
             automation_tasks=list(tasks),
             share_links=share_links,
             configurations=list(configs),
@@ -132,6 +135,11 @@ class BackupService:
             if payload.share_links
             else []
         )
+        user_accounts = (
+            cls._parse_datetime_fields(payload.user_accounts, ["created_at", "last_login"])
+            if payload.user_accounts
+            else []
+        )
         ai_providers = (
             cls._parse_datetime_fields(payload.ai_providers, ["created_at", "updated_at"])
             if payload.ai_providers
@@ -189,10 +197,10 @@ class BackupService:
 
             if "user_accounts" in sections and payload.user_accounts:
                 if mode == "merge":
-                    await cls._merge_records(UserAccount, payload.user_accounts, conn)
+                    await cls._merge_records(UserAccount, user_accounts, conn)
                 else:
                     await UserAccount.bulk_create(
-                        [UserAccount(**user) for user in payload.user_accounts],
+                        [UserAccount(**user) for user in user_accounts],
                         using_db=conn,
                     )