diff --git a/huixiangdou/primitive/bm250kapi.py b/huixiangdou/primitive/bm250kapi.py
index cae1a11..9a5b21f 100644
--- a/huixiangdou/primitive/bm250kapi.py
+++ b/huixiangdou/primitive/bm250kapi.py
@@ -67,6 +67,8 @@ def _tokenize_corpus(self, corpus):
 
     def save(self, chunks:List[Chunk], filedir:str):
         # generate idf with corpus
+        if len(chunks) < 1:
+            return
         self.chunks = chunks
 
         filtered_corpus = []