代码：

<input id="depts">
<script type="text/javascript">
$(document).ready(function() {
$('#depts').combotree({
url: 'data/depts.json',
multiple:true,//复选框
checkbox:true,//
cascadeCheck:false//true:选中父节点后下面的所有子节点选中，false:选中父节点后下面的子节点不选中
});
});
</script>

或者
<input id="depts" name="depts" class="easyui-combotree" data-options="url:'data/depts.json',method:'get',required:true,multiple:true,checkbox:true,cascadeCheck:true">

depts.json模拟数据：

[
{
"children": [
{
"id": "11",
"text": "二级部门1"
},{
"id": "12",
"text": "二级部门2"
},{
"id": "13",
"text": "二级部门3"
},{
"id": "14",
"text": "二级部门4"
}
],
"icoCls": "icon-ok",
"id": "1",
"state": "closed",
"text": "部门1"
},
{
"children": [
{
"id": "21",
"text": "二级部门5"
}
],
"icoCls": "icon-ok",
"id": "2",
"state": "closed",
"text": "部门2"
},
{
"children": [
{
"id": "31",
"text": "二级部门6"
},
{
"id": "32",
"text": "二级部门7"
},
{
"id": "33",
"text": "二级部门8"
}
],
"icoCls": "icon-ok",
"id": "3",
"state": "closed",
"text": "部门3"
}
]