diff --git a/service/book.go b/service/book.go
index 11c3830..758f1ec 100644
--- a/service/book.go
+++ b/service/book.go
@@ -77,7 +77,7 @@ func (s *BookService) GetProCode(req systemReq.GetCodeRequest) (string, error) {
 	input := req.BookName + req.Author + req.Publisher
 	hash := md5.Sum([]byte(input))
 	hexStr := hex.EncodeToString(hash[:])
-	code := hexStr[:19]
+	code := hexStr[:20]
 	return strings.ToUpper(code), nil
 }