var zNodes = "";

        var setting = {

            check: {

                enable: true

            },

            data: {//数据加载

                keep: {

                    parent: true,

                    leaf: true

                },

                simpleData: {

                    enable: true,

                    idKey: "Id",

                    pIdKey: "Pid",

                },

                key: {

                    name: "Name"

                }

            }

        };

function Inint() {//初始化加载节点

            $.ajax({

                global: true,

                async: false,

                cache: false,

                dataType: "json",

                url: '../Ajax/test.ashx',

                type: "post",

                //data: { "roleId": GetQueryString("roleId") },

                success: function (data) {

                    zNodes = data;

                }

            });

        };

$(function () {

            Inint(); //加载数据

            $.fn.zTree.init($("#zTree"), setting, zNodes); 

            var treeObj = $.fn.zTree.getZTreeObj("zTree");

            var nodes = treeObj.getNodes();

            for (var i = 0; i < nodes.length; i++) { //设置节点展开

                treeObj.expandNode(nodes[i], true, false, true);

            }

        });

<div class="control" style="overflow: auto; height:270px;">

            <ul id="zTree">

            </ul>

</div>