diff --git a/src/Align.tsx b/src/Align.tsx
index d8b4048..636b493 100644
--- a/src/Align.tsx
+++ b/src/Align.tsx
@@ -3,16 +3,16 @@
  *  - childrenProps
  */
 
-import React from 'react';
-import { composeRef } from 'rc-util/lib/ref';
-import isVisible from 'rc-util/lib/Dom/isVisible';
 import { alignElement, alignPoint } from 'dom-align';
-import addEventListener from 'rc-util/lib/Dom/addEventListener';
 import isEqual from 'lodash/isEqual';
+import addEventListener from 'rc-util/lib/Dom/addEventListener';
+import isVisible from 'rc-util/lib/Dom/isVisible';
+import { composeRef } from 'rc-util/lib/ref';
+import React from 'react';
 
-import { isSamePoint, restoreFocus, monitorResize } from './util';
-import type { AlignType, AlignResult, TargetType, TargetPoint } from './interface';
 import useBuffer from './hooks/useBuffer';
+import type { AlignResult, AlignType, TargetPoint, TargetType } from './interface';
+import { isSamePoint, monitorResize, restoreFocus } from './util';
 
 type OnAlign = (source: HTMLElement, result: AlignResult) => void;
 
@@ -26,11 +26,6 @@ export interface AlignProps {
   children: React.ReactElement;
 }
 
-interface MonitorRef {
-  element?: HTMLElement;
-  cancel: () => void;
-}
-
 export interface RefAlign {
   forceAlign: () => void;
 }
@@ -52,6 +47,8 @@ const Align: React.ForwardRefRenderFunction<RefAlign, AlignProps> = (
   const cacheRef = React.useRef<{ element?: HTMLElement; point?: TargetPoint; align?: AlignType }>(
     {},
   );
+
+  /** Popup node ref */
   const nodeRef = React.useRef();
   let childNode = React.Children.only(children);
 
@@ -75,9 +72,10 @@ const Align: React.ForwardRefRenderFunction<RefAlign, AlignProps> = (
       align: latestAlign,
       onAlign: latestOnAlign,
     } = forceAlignPropsRef.current;
-    if (!latestDisabled && latestTarget) {
-      const source = nodeRef.current;
 
+    const source = nodeRef.current;
+
+    if (!latestDisabled && latestTarget && source) {
       let result: AlignResult;
       const element = getElement(latestTarget);
       const point = getPoint(latestTarget);
@@ -110,40 +108,32 @@ const Align: React.ForwardRefRenderFunction<RefAlign, AlignProps> = (
   }, monitorBufferTime);
 
   // ===================== Effect =====================
-  // Listen for target updated
-  const resizeMonitor = React.useRef<MonitorRef>({
-    cancel: () => {},
-  });
-  // Listen for source updated
-  const sourceResizeMonitor = React.useRef<MonitorRef>({
-    cancel: () => {},
-  });
-  React.useEffect(() => {
-    const element = getElement(target);
-    const point = getPoint(target);
-
-    if (nodeRef.current !== sourceResizeMonitor.current.element) {
-      sourceResizeMonitor.current.cancel();
-      sourceResizeMonitor.current.element = nodeRef.current;
-      sourceResizeMonitor.current.cancel = monitorResize(nodeRef.current, forceAlign);
-    }
+  // Handle props change
+  const element = getElement(target);
+  const point = getPoint(target);
 
+  React.useEffect(() => {
     if (
       cacheRef.current.element !== element ||
       !isSamePoint(cacheRef.current.point, point) ||
       !isEqual(cacheRef.current.align, align)
     ) {
       forceAlign();
-
-      // Add resize observer
-      if (resizeMonitor.current.element !== element) {
-        resizeMonitor.current.cancel();
-        resizeMonitor.current.element = element;
-        resizeMonitor.current.cancel = monitorResize(element, forceAlign);
-      }
     }
   });
 
+  // Watch popup element resize
+  React.useEffect(() => {
+    const cancelFn = monitorResize(nodeRef.current, forceAlign);
+    return cancelFn;
+  }, [nodeRef.current]);
+
+  // Watch target element resize
+  React.useEffect(() => {
+    const cancelFn = monitorResize(element, forceAlign);
+    return cancelFn;
+  }, [element]);
+
   // Listen for disabled change
   React.useEffect(() => {
     if (!disabled) {
@@ -154,24 +144,17 @@ const Align: React.ForwardRefRenderFunction<RefAlign, AlignProps> = (
   }, [disabled]);
 
   // Listen for window resize
-  const winResizeRef = React.useRef<{ remove: Function }>(null);
   React.useEffect(() => {
     if (monitorWindowResize) {
-      if (!winResizeRef.current) {
-        winResizeRef.current = addEventListener(window, 'resize', forceAlign);
-      }
-    } else if (winResizeRef.current) {
-      winResizeRef.current.remove();
-      winResizeRef.current = null;
+      const cancelFn = addEventListener(window, 'resize', forceAlign);
+
+      return cancelFn.remove;
     }
   }, [monitorWindowResize]);
 
   // Clear all if unmount
   React.useEffect(
     () => () => {
-      resizeMonitor.current.cancel();
-      sourceResizeMonitor.current.cancel();
-      if (winResizeRef.current) winResizeRef.current.remove();
       cancelForceAlign();
     },
     [],
diff --git a/tests/element.test.tsx b/tests/element.test.tsx
index 742761c..86d68ab 100644
--- a/tests/element.test.tsx
+++ b/tests/element.test.tsx
@@ -1,7 +1,7 @@
 /* eslint-disable class-methods-use-this */
-import React from 'react';
-import { render } from '@testing-library/react';
+import { act, render } from '@testing-library/react';
 import { spyElementPrototype } from 'rc-util/lib/test/domHook';
+import React from 'react';
 import Align from '../src';
 
 describe('element align', () => {
@@ -16,6 +16,7 @@ describe('element align', () => {
   });
 
   afterEach(() => {
+    jest.clearAllTimers();
     jest.useRealTimers();
   });
 
diff --git a/tests/strict.test.tsx b/tests/strict.test.tsx
new file mode 100644
index 0000000..fa87689
--- /dev/null
+++ b/tests/strict.test.tsx
@@ -0,0 +1,78 @@
+/* eslint-disable class-methods-use-this */
+import { act, render } from '@testing-library/react';
+import { spyElementPrototype } from 'rc-util/lib/test/domHook';
+import React from 'react';
+import Align from '../src';
+
+(global as any).watchCnt = 0;
+
+jest.mock('../src/util', () => {
+  const originUtil = jest.requireActual('../src/util');
+
+  return {
+    ...originUtil,
+    monitorResize: (...args: any[]) => {
+      (global as any).watchCnt += 1;
+      const cancelFn = originUtil.monitorResize(...args);
+
+      return () => {
+        (global as any).watchCnt -= 1;
+        cancelFn();
+      };
+    },
+  };
+});
+
+describe('element align', () => {
+  beforeAll(() => {
+    spyElementPrototype(HTMLElement, 'offsetParent', {
+      get: () => ({}),
+    });
+  });
+
+  beforeEach(() => {
+    jest.useFakeTimers();
+  });
+
+  afterEach(() => {
+    jest.clearAllTimers();
+    jest.useRealTimers();
+  });
+
+  it('StrictMode should keep resize observer', () => {
+    const Demo = () => {
+      const targetRef = React.useRef(null);
+
+      return (
+        <>
+          <div ref={targetRef} />
+          <Align target={() => targetRef.current} align={{ points: ['bc', 'tc'] }}>
+            <div
+              style={{
+                position: 'absolute',
+                width: 50,
+                height: 80,
+              }}
+            />
+          </Align>
+        </>
+      );
+    };
+
+    const { unmount } = render(
+      <React.StrictMode>
+        <Demo />
+      </React.StrictMode>,
+    );
+
+    act(() => {
+      jest.runAllTimers();
+    });
+
+    expect((global as any).watchCnt).toBeGreaterThan(0);
+
+    unmount();
+    expect((global as any).watchCnt).toEqual(0);
+  });
+});
+/* eslint-enable */