diff --git a/app/common/service/UsedCarService.php b/app/common/service/UsedCarService.php
index 0e44fd0..bffec12 100644
--- a/app/common/service/UsedCarService.php
+++ b/app/common/service/UsedCarService.php
@@ -94,7 +94,11 @@ class UsedCarService
         if(empty($data['price'])){
             $data['price'] = 0;
         }
-        $data['attachment'] = json_encode($data['attachment']);
+        if(!empty($data['attachment'])){
+            $data['attachment'] = json_encode($data['attachment']);
+        }else{
+            $data['attachment'] = '';
+        }
         $data['user_id'] = $request->user['id'];
         return $data;
     }