前台datagrid获取json数据为什么显示了纯JSON字符串？

前台: $(function(){
$('#JzUserList').treegrid({
title:'TreeGrid',
iconCls:'icon-save',
width:500,
height:350,
nowrap: false,
rownumbers: true,
animate:true,
collapsible:true,
url:'Deafult.aspx',
idField:'JzUserID',
treeField:'id',
frozenColumns:[[
                {title:'编号',field:'JzUserID',width:150,
                formatter:function(value){
                 return '<span style="color:red">'+value+'</span>';
                }
                }
]],
columns:[[
{field:'UserName',title:'Name',width:120},
{field:'Birth',title:'Address',width:120,rowspan:2},
{field:'BirthAddress',title:'Col41',width:150,rowspan:2}
]]
});
});后台json数据：[{"JzUserID":"2","UserName":"朱家林","Birth":"1991/9/27 0:00:00","BirthAddress":"安徽巢湖","CommAddress":"安徽合肥","CardNumber":"341182199109281716","TelePhone":"13156502121","Mobile":"13133222211","CardPic":"image.gif","UserPic":"src.gif","PostCode":"238000","Culturaldegree":"3","PoliticalAffiliation":"2","Sex":"1","Hobby":"游泳","ReligiousBeliefs":"2","BelongsCmyID":"2","Health":"1","EmploymentType":"2","EmployKind":"月嫂,钟点工","RegistTime":"2011/3/2 17:33:15","FamilyName":"汉","IssuingAuthority":"","ExpiringDate":"2010年2月-2030年2月"},{"JzUserID":"1","UserName":"郑辉","Birth":"1990/1/1 0:00:00","BirthAddress":"安徽宣称","CommAddress":"安徽合肥","CardNumber":"341182199109281716","TelePhone":"13156502121","Mobile":"13133222211","CardPic":"image.gif","UserPic":"src.gif","PostCode":"238000","Culturaldegree":"3","PoliticalAffiliation":"2","Sex":"1","Hobby":"游泳","ReligiousBeliefs":"1","BelongsCmyID":"1","Health":"1","EmploymentType":"1","EmployKind":"月嫂,钟点工","RegistTime":"2011/3/2 17:33:15","FamilyName":"汉","IssuingAuthority":"合肥公安局","ExpiringDate":"2010年2月-2030年2月"}]