效果图：

 

代码： 

<template>
  <div class="agency-wrap">
    <el-tree
      class="filter-tree"
      :data="detailList"
      :props="defaultProps"
      default-expand-all
      @node-click="onClickNode"
      :filter-node-method="filterNode"
      ref="tree">
    </el-tree>
  </div>
</template>

<script>
export default {
  data () {
    return {
      detailList: [{
        id: 1,
        label: '一级 1',
        children: [{
          id: 4,
          label: '二级 1-1',
          children: [{
            id: 9,
            label: '三级 1-1-1'
          }, {
            id: 10,
            label: '三级 1-1-2'
          }]
        }]
      }, {
        id: 2,
        label: '一级 2',
        children: [{
          id: 5,
          label: '二级 2-1'
        }, {
          id: 6,
          label: '二级 2-2'
        }]
      }, {
        id: 3,
        label: '一级 3',
        children: [{
          id: 7,
          label: '二级 3-1'
        }, {
          id: 8,
          label: '二级 3-2'
        }]
      }],
      defaultProps: {
        children: 'children',
        label: 'label'
      }
    }
  },
  methods: {
    onClickNode (data) {
      console.log(data)
    },
    filterNode (value, data) {
      if (!value) return true
      return data.label.indexOf(value) !== -1
    }
  }
}
</script>

<style lang="scss" scoped>
.agency-wrap {
  @include wh(100%, 200px);
  background-color: pink;
  overflow: auto;
  margin-bottom: 20px;
  ::v-deep .el-tree-node__label {
    font-size: 6px;
  }
  ::v-deep {
    .el-icon-arrow-right::before {
      font-size: 6px;
    }
  }
  ::v-deep .el-tree > .el-tree-node:after {
    border-top: none;
  }

  ::v-deep .el-tree-node {
    position: relative;
    padding-left: 5px;
  }

  ::v-deep .el-tree-node__children {
    padding-left: 5px;
  }

  ::v-deep .el-tree-node :last-child:before {
    height: 16px;
  }

  ::v-deep .el-tree-node:before {
    content: '';
    left: -2px;
    position: absolute;
    right: auto;
    border-width: .5px;
  }

  ::v-deep .el-tree-node:after {
    content: '';
    left: -2px;
    position: absolute;
    right: auto;
    border-width: .5px;
  }

  ::v-deep .el-tree-node:before {
    border-left: .5px dashed #1389BC;
    bottom: 0px;
    height: 100%;
    top: -13px;
    width: .5px;
  }

  ::v-deep .el-tree {
    //   overflow-y: auto;
    //   overflow-x: scroll;
    overflow: auto;
    height: 100%;
    /*width:200px;*/
    //   border: 1px solid blue;
  }

  ::v-deep .el-tree-node:after {
    border-top: .5px dashed #1389BC;
    height: 10px;
    top: 6px;
    width: 9px;
  }

  ::v-deep .el-tree .el-tree-node__expand-icon.expanded {
    -webkit-transform: rotate(0deg);
    transform: rotate(0deg);
  }

  ::v-deep .el-tree .el-icon-caret-right:before {
    content: "\e723";
    font-size: 8px;
    color: #1389BC;
    position: absolute;
    left: -6px;
    top: -4px;
  }

  ::v-deep .el-tree .el-tree-node__expand-icon.expanded.el-icon-caret-right:before {
    content: "\e722";
    font-size: 8px;
    color: #1389BC;
    position: absolute;
    left: -6px;
    top: -4px;
  }

  ::v-deep .el-tree-node__content > .el-tree-node__expand-icon {
    padding: 0;
    padding-left: 8px;
  }
}
</style>