diff --git a/components/dialog/index.spec.ts b/components/dialog/index.spec.ts
index 38e0e8c3c..bec4d1e02 100644
--- a/components/dialog/index.spec.ts
+++ b/components/dialog/index.spec.ts
@@ -337,6 +337,36 @@ describe('Dialog', () => {
         expect(dialog2.querySelector('.k-dialog-body')!.textContent).to.eql('test');
     });
 
+    it('should update position when change container', async () => {
+        class Demo extends Component<{show: boolean, container: any}> {
+            static template = `
+                var Dialog = this.Dialog;
+                <Dialog value={true} container={this.get('container')} ref="dialog">test</Dialog>
+            `;
+
+            private Dialog = Dialog;
+
+            static defaults() {
+                return {
+                    container: (parentDom: HTMLElement) => parentDom,
+                };
+            }
+        }
+
+        const [instance, element] = mount(Demo);
+
+        await wait();
+        instance.set('container', undefined);
+        await wait();
+        const dialogDom = instance.refs.dialog.dialogRef.value;
+        const style = dialogDom.style;
+        expect(style.left).not.eql('');
+        expect(style.top).not.eql('');
+
+        // should append to body
+        expect(dialogDom.closest('.k-dialog-wrapper').parentElement).to.eql(document.body);
+    });
+
     // it('should handle v-if and v-model at the same time correctly in Vue', async () => {
         // const Test = {
             // template: `<Dialog v-model="show" v-if="show" ref="dialog">test</Dialog>`,
diff --git a/components/dialog/usePosition.ts b/components/dialog/usePosition.ts
index 278ff29d3..3b7296b2a 100644
--- a/components/dialog/usePosition.ts
+++ b/components/dialog/usePosition.ts
@@ -8,6 +8,10 @@ export function usePosition(elementRef: RefObject<HTMLDivElement>) {
 
     instance.on(SHOW, center);
     instance.on('afterClose', onAfterLeave);
+    instance.watch('container', () => {
+        if (!instance.get('value')) return;
+        center();
+    }, { presented: true, inited: true });
 
     function center() {
         position(elementRef.value!, {
diff --git a/components/dropdown/usePosition.ts b/components/dropdown/usePosition.ts
index d0d5b9db5..e2c1c0d40 100644
--- a/components/dropdown/usePosition.ts
+++ b/components/dropdown/usePosition.ts
@@ -1,8 +1,7 @@
 import {useInstance, findDomFromVNode} from 'intact';
 import type {Dropdown} from './';
 import {Options, position, Feedback} from '../position';
-import {noop} from 'intact-shared';
-import {isObject} from 'intact-shared';
+import {noop, isObject, isFunction} from 'intact-shared';
 import { isEqualObject } from '../utils';
 
 export type FeedbackCallback = (feedback: Feedback) => void;
@@ -19,21 +18,32 @@ export function usePosition() {
 
     (['of', 'position'] as const).forEach(item => {
         instance.watch(item, (newValue, oldValue) => {
-            // return if object is the same
             if (
+                instance.get('value') ||
+                // return if object is the same
                 isObject(newValue) && isObject(oldValue) &&
                 // is not event object
                 !(newValue instanceof Event) &&
                 isEqualObject(newValue, oldValue)
-            )  {
-                return;
-            }
-            if (instance.get('value')) {
-                handle(noop);
-            }
+            ) return;
+
+            handle(noop);
         }, {presented: true, inited: true});
     });
 
+    // watch container, it is not commonly used
+    instance.watch('container', (newValue, oldValue) => {
+        if (
+            !instance.get('value') ||
+            // return if function is the same. Not rigorous!
+            isFunction(newValue) &&
+            isFunction(oldValue) &&
+            newValue.toString() === oldValue.toString()
+        ) return;
+
+        handle(noop);
+    }, { presented: true, inited: true });
+
     // if the dropdown is nested, we must show child after parent has positioned
     function p(
         ofElement: HTMLElement | MouseEvent | undefined,
diff --git a/components/portal.ts b/components/portal.ts
index 6983998dc..22816cb97 100644
--- a/components/portal.ts
+++ b/components/portal.ts
@@ -151,7 +151,11 @@ export class Portal<T extends PortalProps = PortalProps> extends Component<T> {
             } else {
                 this.container = container(parentDom, anchor);
             }
+        } else {
+            // let below logic to set container to default if container does not exist.
+            this.container = null;
         }
+
         if (!this.container) {
             if (this.$senior instanceof BaseDialog) {
                 // Dialog and Drawer must be inserted into document.body