diff --git a/jieba/analyse/__init__.py b/jieba/analyse/__init__.py
index ea7e66c..c56b9a4 100755
--- a/jieba/analyse/__init__.py
+++ b/jieba/analyse/__init__.py
@@ -59,14 +59,14 @@ def set_stop_words(stop_words_path):
     for line in lines:
         STOP_WORDS.add(line)
 
-def extract_tags(sentence, topK=20, withWeight=False, allowPOS=[]):
+def extract_tags(sentence, topK=20, withWeight=False, allowPOS=['ns', 'n', 'vn', 'v']):
     """
     Extract keywords from sentence using TF-IDF algorithm.
     Parameter:
         - topK: return how many top keywords. `None` for all possible words.
         - withWeight: if True, return a list of (word, weight);
                       if False, return a list of words.
-        - allowPOS: the allowed POS list eg. ['n'].
+        - allowPOS: the allowed POS list eg. ['ns', 'n', 'vn', 'v'].
                     if the POS of w is not in this list,it will be filtered.
     """
     global STOP_WORDS, idf_loader
diff --git a/jieba/analyse/textrank.py b/jieba/analyse/textrank.py
index 9ac9ece..739c60e 100644
--- a/jieba/analyse/textrank.py
+++ b/jieba/analyse/textrank.py
@@ -48,15 +48,17 @@ class UndirectWeightedGraph:
         return ws
 
 
-def textrank(sentence, topK=10, withWeight=False):
+def textrank(sentence, topK=10, withWeight=False, allowPOS=['ns', 'n', 'vn', 'v']):
     """
     Extract keywords from sentence using TextRank algorithm.
     Parameter:
         - topK: return how many top keywords. `None` for all possible words.
         - withWeight: if True, return a list of (word, weight);
                       if False, return a list of words.
+        - allowPOS: the allowed POS list eg. ['ns', 'n', 'vn', 'v'].
+                    if the POS of w is not in this list,it will be filtered.
     """
-    pos_filt = frozenset(('ns', 'n', 'vn', 'v'))
+    pos_filt = frozenset(allowPOS)
     g = UndirectWeightedGraph()
     cm = collections.defaultdict(int)
     span = 5