设置 class="treeClass" show-icon

  <a-tree
                v-if="treeData.length > 0"
                :show-line="true"
                :tree-data="treeData"
                show-icon
                ref="tree"
                class="treeClass"
                :defaultExpandAll="true"
                :replace-fields="replaceFields"
                :auto-expand-parent="autoExpandParent"
                :expanded-keys="expandedKeys"
                @expand="onExpand"
            >

.treeClass {
    //a-tree图标
        /deep/.ant-tree-switcher-line-icon {
        display: none;
         }
   //关闭时的图
    /deep/.ant-tree-switcher_close {
        // width: 16px !important;
        // height: 15px !important;
        background: url('图片地址') no-repeat !important;
        background-size: 100% 100% !important;
    }

    //展开时的图
    /deep/.ant-tree-switcher_open {
        // width: 16px !important;
        // height: 15px !important;
        background: url('图片地址') no-repeat !important;
        background-size: 100% 100% !important;
    }
//最后一级的图
    /deep/.ant-tree-switcher-noop{
        background: url('图片地址') no-repeat !important;
        background-size: 100% 100% !important;
    }
 
}


/*隐藏树的默认竖线*/
//   /deep/.treeClass.ant-tree-show-line li:not(:last-child):before {
//     border-left: 0px;
//   }