diff --git a/qcloud_cos/cos_op.py b/qcloud_cos/cos_op.py
index 1af40d8..16fa7b5 100644
--- a/qcloud_cos/cos_op.py
+++ b/qcloud_cos/cos_op.py
@@ -371,7 +371,8 @@ def _upload_slice_file(self, request):
 
         local_path = request.get_local_path()
         file_size = os.path.getsize(local_path)
-        slice_size = control_ret[u'data'][u'slice_size']
+        if u'slice_size' in control_ret[u'data']:
+            slice_size = control_ret[u'data'][u'slice_size']
         offset = 0
         session = control_ret[u'data'][u'session']
         # ?concurrency