1、<style> 不要添加 “scoped” 属性

2、css

  .el-tree-node:focus > .el-tree-node__content {
    background-color: #66b1ff87 !important;
  }
  .el-tree-node__content:hover {    background-color: #66b1ff87;
  }
  .el-tree--highlight-current .el-tree-node.is-current>.el-tree-node__content {
    background-color: #66b1ff87;
  }

效果：