diff --git a/paddlehub/tokenizer/tokenizer.py b/paddlehub/tokenizer/tokenizer.py
index 4ad6db48cf0f9da4da9b8c7285cad96d0d2bf974..f2f9111a1fbd974cb6ac1801a604d766228f29b0 100644
--- a/paddlehub/tokenizer/tokenizer.py
+++ b/paddlehub/tokenizer/tokenizer.py
@@ -78,7 +78,11 @@ class CustomTokenizer(object):
 
     def _convert_token_to_id(self, token):
         """ Converts a token (str) in an id using the vocab. """
-        return self.vocab.get(token, None)
+        v = self.vocab.get(token, None)
+        if v:
+            return v
+        else:
+            return 0
 
     def _convert_id_to_token(self, index):
         """Converts an index (integer) in a token (str) using the vocab."""
@@ -123,8 +127,8 @@ class CustomTokenizer(object):
         ids = []
         for token in tokens:
             wid = self._convert_token_to_id(token)
-            if wid:
-                ids.append(self._convert_token_to_id(token))
+            if wid is not None:
+                ids.append(wid)
         return ids
 
     def tokenize(self, text):
@@ -204,14 +208,14 @@ class CustomTokenizer(object):
             if isinstance(text, str):
                 tokens = self.tokenize(text)
                 ids = self.convert_tokens_to_ids(tokens)
-                return self.convert_tokens_to_ids(tokens)
+                return ids
             elif isinstance(text,
                             (list, tuple)) and len(text) > 0 and isinstance(
-                                text[0], str):
+                text[0], str):
                 return self.convert_tokens_to_ids(text)
             elif isinstance(text,
                             (list, tuple)) and len(text) > 0 and isinstance(
-                                text[0], int):
+                text[0], int):
                 return text
             else:
                 raise ValueError(
@@ -350,7 +354,7 @@ class CustomTokenizer(object):
         """
         out_string = (out_string.replace(" .", ".").replace(" ?", "?").replace(
             " !", "!").replace(" ,", ",").replace(" ' ", "'").replace(
-                " n't",
-                "n't").replace(" 'm", "'m").replace(" 's", "'s").replace(
-                    " 've", "'ve").replace(" 're", "'re"))
+            " n't",
+            "n't").replace(" 'm", "'m").replace(" 's", "'s").replace(
+            " 've", "'ve").replace(" 're", "'re"))
         return out_string