diff --git a/src/layouts/Header.less b/src/layouts/Header.less
index 3bd5b523..8f5fcb9e 100644
--- a/src/layouts/Header.less
+++ b/src/layouts/Header.less
@@ -3,4 +3,5 @@
   top: 0;
   width: 100%;
   z-index: 9;
+  transition: width 0.2s;
 }