1、在生成tree的json数据中，直接给出：open:true的属性;
2、treeObj.expandAll(true);
3、var zTree = $.fn.zTree.getZTreeObj("ztree");
var node=zTree.getNodeByParam("OrgID", 0);
zTree.selectNode(node);
zTree.expandNode(node, true, false, false);
原文：http://www.cnblogs.com/mahao1993/p/6649608.html