diff --git a/backend/app/admin/service/file_service.py b/backend/app/admin/service/file_service.py
index 158daef..34a79fd 100755
--- a/backend/app/admin/service/file_service.py
+++ b/backend/app/admin/service/file_service.py
@@ -768,10 +768,10 @@ class FileService:
             content_length = int(content_length) if content_length is not None else (size or 0)
         except:
             content_length = size or 0
-        content_type = head.get('Content-Type') or head.get('ContentType') or mime
+        content_type = mime or head.get('Content-Type') or head.get('ContentType')
         etag = (head.get('ETag') or '').strip('"')
         file_hash_val = sha256 or etag or hashlib.sha256(f"cos:{cloud_path}:{file_id_in_cos}".encode()).hexdigest()
-        is_image = (content_type or '').lower().startswith('image/') or (mime or '').lower().startswith('image/')
+        is_image = (mime or '').lower().startswith('image/') or (content_type or '').lower().startswith('image/')
         if is_image:
             avif_key = f"{file_id}_avif"
             pic_ops = {