diff --git a/python/paddle/fluid/trainer_desc.py b/python/paddle/fluid/trainer_desc.py
index ffef35b7acc2769495a91e412fa2373552a2f71e..478e05c8975d06d602253d692114f77ca25de0af 100644
--- a/python/paddle/fluid/trainer_desc.py
+++ b/python/paddle/fluid/trainer_desc.py
@@ -49,6 +49,8 @@ class TrainerDesc(object):
         self._infer = False
 
     def _set_fetch_var_and_info(self, fetch_vars, fetch_info, print_period):
+        # convert fetch_info to list
+        fetch_info = list(fetch_info)
         for i, v in enumerate(fetch_vars):
             self.proto_desc.fetch_config.fetch_var_names.extend([v.name])
             self.proto_desc.fetch_config.fetch_var_str_format.extend(