效果图：

代码：

import React from "react";
import ReactDOM from "react-dom";
import "antd/dist/antd.css";
import { TreeSelect } from "antd";
 
const { TreeNode } = TreeSelect;
 
class Demo extends React.Component {
  state = {
    defaultDataList: [], // 存所有的末级子节点
    allPlaceholder: '全部',
  };
 
   onChange = (values) => {
    const { defaultDataList } = this.state;
    this.setState({ allPlaceholder:  values.length === defaultDataList.length ? '全部' : null});
  }
 
  render() {
    return (
      <TreeSelect
            dropdownStyle={
   
   { maxHeight: 400, overflow: 'auto' }}
            treeData={deptTree}
            allowClear
            showSearch
            treeNodeFilterProp="title"
            multiple
            treeCheckable
            placeholder={placeholder || "请选择"}
            treeDefaultExpandAll="true"
            onChange={this.onChange}
            maxTagCount={allPlaceholder ? 0 : 2}
            maxTagPlaceholder={allPlaceholder}
          />
    );
  }
}
 
ReactDOM.render(<Demo />, document.getElementById("container"));    

主要是maxTagCount和maxTagPlaceholder实现的