diff --git a/public/docs/ts/latest/tutorial/toh-pt4.jade b/public/docs/ts/latest/tutorial/toh-pt4.jade
index c356ad2b65..81ff2bd42d 100644
--- a/public/docs/ts/latest/tutorial/toh-pt4.jade
+++ b/public/docs/ts/latest/tutorial/toh-pt4.jade
@@ -597,3 +597,6 @@ p 运行这部分的#[+liveExampleLink2('在线例子', 'toh-4')]。
   
   Back in the `AppComponent`, replace `heroService.getHeroes` with `heroService.getHeroesSlowly`
   and see how the app behaves.
+
+  回到`AppComponent`，用`heroService.getHeroesSlowly`替换掉`heroService.getHeroes`，并观察本应用的行为。
+