在树初始化时，加一个load图片

做个浮动图层放在 zTree 上面， 然后利用 asnycSuccess 和 asyncError 回调捕获 ajax加载完毕，这时候让你的loading图层隐藏

<SCRIPT LANGUAGE="JavaScript">
		<!--
		var setting = {
			async: {
				enable: true,
				url:"http://localhost:8080/../TtreeKode",
				autoParam:["id", "name=n","url"],
				expandSpeed:false,				
				dataFilter: filter
			},
			callback: {
			    onClick: onClick,
				beforeAsync: beforeAsync,
				onCollapse: onCollapse,
				onExpand: onExpand,
				onAsyncSuccess:zTreeOnAsyncSuccess
			}
		};
		
		function getTime() {
			var now= new Date(),
			h=now.getHours(),
			m=now.getMinutes(),
			s=now.getSeconds(),
			ms=now.getMilliseconds();
			return (h+":"+m+":"+s+ " " +ms);
		}
		
		function onCollapse(event, treeId, treeNode) {
			//alert("onCollapse: " + treeId + "," + treeNode.name + "," + treeNode.id+ "," + treeNode.url);
		}		
		
		function onExpand(event, treeId, treeNode) {
			//alert("onExpand: " + treeId + "," + treeNode.name+ "," + treeNode.id+ "," + treeNode.url);
		}
		
		function onClick(event, treeId, treeNode, clickFlag) {
		    alert(treeNode.name);
			//alert("onClick: " + treeId + "," + treeNode.name + "," + clickFlag+ "," + treeNode.id+ "," + treeNode.url);
		}		

		function filter(treeId, parentNode, childNodes) {
			if (!childNodes) return null;
			for (var i=0, l=childNodes.length; i<l; i++) {
				childNodes[i].name = childNodes[i].name.replace(/\.n/g, '.');
			}
			return childNodes;
		}
		function beforeAsync(treeId, treeNode) {
			return treeNode ? treeNode.level < 5 : true;
		}
		关键点--->
		function zTreeOnAsyncSuccess(event,treeId, treeNode, msg) {
			//alert(msg);
			style="display: none;"
            document.getElementById("process").style.display="none";
            document.getElementById("treeDemo").style.visibility="visible";
		}

		$(document).ready(function(){
			$.fn.zTree.init($("#treeDemo"), setting);
			 document.getElementById("treeDemo").style.visibility="hidden";
		});
		//-->
	</SCRIPT>

<ul id="process" class="ztree"><img id='loadingImg' style='margin-left:30px;' src='<%=basePath%>helloword/img/03.gif' /></ul>
  	  <ul id="treeDemo" class="ztree"></ul>