css中加入
/deep/ .el-scrollbar__view{display:inline-block !important;}
/deep/ .el-scrollbar__wrap{overflow-x: hidden !important;}

//html
el-scrollbar.left
  el-tree(
    :data="treeData" 
    node-key="id"
    ref="treeRef"
    default-expand-all
    @node-click="handleNodeClick"
  )

//css
.left {
  border-right: 1px solid #EBEEF5;height: calc(100vh - 66px);
  width: 330px; margin-left: 10px;
  /deep/ .el-scrollbar__view{display:inline-block !important;}
  /deep/ .el-scrollbar__wrap{overflow-x: hidden !important;}
}