diff --git a/lib/text_filter.py b/lib/text_filter.py
index 5ded82c..296af69 100644
--- a/lib/text_filter.py
+++ b/lib/text_filter.py
@@ -43,6 +43,7 @@ class TextFilter(object):
     
     # Singleton
     _instance = None
+    root = None
     
     def __new__(cls, *args, **kw):
         """单例模式"""
@@ -51,11 +52,12 @@ class TextFilter(object):
         return cls._instance
     
     def __init__(self):
-        self.root = Node()
-        self.sensitive_word = SensitiveWords().sensitive_word_dict
-        for word_type in self.sensitive_word.keys():
-            for word in self.sensitive_word[word_type]:
-                self.add_word(word, word_type)
+        if self.root == None:
+            self.root = Node()
+            self.sensitive_word = SensitiveWords().sensitive_word_dict
+            for word_type in self.sensitive_word.keys():
+                for word in self.sensitive_word[word_type]:
+                    self.add_word(word, word_type)
     
     def add_word(self, word, word_type=u'common'):
         """向字典树里添加敏感词汇及敏感词类型"""