ant-design/components/modal/demo/position.tsx

import React, { useState } from 'react';
import { Button, Modal } from 'antd';

const App: React.FC = () => {
  const [modal1Open, setModal1Open] = useState(false);
  const [modal2Open, setModal2Open] = useState(false);

  return (
    <>
      <Button type="primary" onClick={() => setModal1Open(true)}>
        Display a modal dialog at 20px to Top
      </Button>
      <Modal
        title="20px to Top"
        style={{ top: 20 }}
        open={modal1Open}
        onOk={() => setModal1Open(false)}
        onCancel={() => setModal1Open(false)}
      >
        <p>some contents...</p>
        <p>some contents...</p>
        <p>some contents...</p>
      </Modal>
      <br />
      <br />
      <Button type="primary" onClick={() => setModal2Open(true)}>
        Vertically centered modal dialog
      </Button>
      <Modal
        title="Vertically centered modal dialog"
        centered
        open={modal2Open}
        onOk={() => setModal2Open(false)}
        onCancel={() => setModal2Open(false)}
      >
        <p>some contents...</p>
        <p>some contents...</p>
        <p>some contents...</p>
      </Modal>
    </>
  );
};

export default App;