diff --git a/biliup/plugins/bili_webup.py b/biliup/plugins/bili_webup.py
index 875309f..ee4f338 100644
--- a/biliup/plugins/bili_webup.py
+++ b/biliup/plugins/bili_webup.py
@@ -274,7 +274,7 @@ class BiliBili:
                 timeout=5)
             return asyncio.run(upload(f, total_size, ret.json(), tasks=tasks))
 
-    async def cos(self, file, total_size, ret, chunk_size=4194304, tasks=3):
+    async def cos(self, file, total_size, ret, chunk_size=10485760, tasks=3):
         filename = file.name
         url = ret["url"].replace("accelerate", "ap-shanghai")
         biz_id = ret["biz_id"]