diff --git a/book/book.toml b/book/book.toml
index f9b193d0..a60f64d1 100644
--- a/book/book.toml
+++ b/book/book.toml
@@ -19,3 +19,5 @@ line-numbers = true
 enable = true
 level = 2
 
+[rust]
+edition = "2021"   #在线运行用2021版本的