diff --git a/aio/content/translations/cn/api-plan.md b/aio/content/translations/cn/api-plan.md
index 39bea14773..61d8e10a3c 100644
--- a/aio/content/translations/cn/api-plan.md
+++ b/aio/content/translations/cn/api-plan.md
@@ -76,7 +76,7 @@
 [x]  | router/NavigationStart  | 0.21
 [x]  | common/formatDate  | 0.21
 [x]  | core/ComponentFactoryResolver  | 0.20
-[ ]  | forms/Form  | 0.20
+[x]  | forms/Form  | 0.20
 [ ]  | common/http/HttpErrorResponse  | 0.20
 [ ]  | core/QueryList  | 0.19
 [ ]  | forms  | 0.19
diff --git a/packages/forms/src/directives/form_interface.ts b/packages/forms/src/directives/form_interface.ts
index d2790aa1d8..efa06568b2 100644
--- a/packages/forms/src/directives/form_interface.ts
+++ b/packages/forms/src/directives/form_interface.ts
@@ -16,43 +16,59 @@ import {NgControl} from './ng_control';
 /**
  * An interface that `FormGroupDirective` and `NgForm` implement.
  *
+ * 由 `FormGroupDirective` 和 `NgForm` 实现的接口。
+ *
  * Only used by the forms module.
  *
- *
+ * 只用于表单模块。
  */
 export interface Form {
   /**
    * Add a control to this form.
+   *
+   * 把控件添加到该表单中。
    */
   addControl(dir: NgControl): void;
 
   /**
    * Remove a control from this form.
+   *
+   * 从该表单中移除控件。
    */
   removeControl(dir: NgControl): void;
 
   /**
    * Look up the `FormControl` associated with a particular `NgControl`.
+   *
+   * 查找与指定的 `NgControl` 相关的 `FormControl`。
    */
   getControl(dir: NgControl): FormControl;
 
   /**
    * Add a group of controls to this form.
+   *
+   * 往该表单中添加一组控件。
    */
   addFormGroup(dir: AbstractFormGroupDirective): void;
 
   /**
    * Remove a group of controls from this form.
+   *
+   * 从该表单中移除一组控件。
    */
   removeFormGroup(dir: AbstractFormGroupDirective): void;
 
   /**
    * Look up the `FormGroup` associated with a particular `AbstractFormGroupDirective`.
+   *
+   * 查找与指定的 `AbstractFormGroupDirective` 相关的 `FormGroup`。
    */
   getFormGroup(dir: AbstractFormGroupDirective): FormGroup;
 
   /**
    * Update the model for a particular control with a new value.
+   *
+   * 把指定控件的表单模型修改为新的值。
    */
   updateModel(dir: NgControl, value: any): void;
 }