解决:  destroy: true,   

var tabel = $('#userlist').DataTable({
        destroy: true,                    //加上此属性即可
        bProcessing: true,           //DataTables载入数据时,是否显示‘进度’提示  
        bStateSave: false,          //是否打开客户端状态记录功能,此功能在ajax刷新纪录的时候不会将个性化设定回复为初始化状态  
        aLengthMenu: [10, 20, 40, 60, 100, 1000], //更改显示记录数选项  
        iDisplayLength: 10,        //默认显示的记录数  
        bInfo: true,              //是否显示页脚信息,DataTables插件左下角显示记录数  
        bPaginate: true,         //是否显示(应用)分页器  
        autoWidth: true,        //是否自适应宽度  
        bScrollCollapse: true, //是否开启DataTables的高度自适应,当数据条数不够分页数据条数的时候,插件高度是否随数据条数而改变  
        sPaginationType: "full_numbers", //详细分页组,可以支持直接跳转到某页  
        bSort: false,        //是否启动各个字段的排序功能  
        bFilter: true,      //是否启动过滤、搜索功能        
        bServerSide: true, //开启此模式后,你对datatables的每个操作 每页显示多少条记录、下一页、上一页、排序(表头)、搜索,这些都会传给服务器相应的值。
        "ajax": {
            url: "/Ajax/UserMgrAjax.ashx?cmd=userList",
            type: "POST"

        },
        columns: [
            {
                "sWidth": "4%",
                "sClass": "text-center",
                "data": null,
                "targets": 0
            },
             {
                 "sWidth": "4%",
                 "sClass": "text-center",
                 "data": "u_id",
                 "render": function (data, type, full, meta) {//这里就是要显示的checkbox多选框了
                  
                     return '<input type="checkbox"  class="checkchild"  value="' + data + '" />';
                 },
                 "bSortable": false
             },

              { "sClass": "text-center", "data": "u_name" },
             { "sClass": "text-center", "data": "u_tel" },
             {
                 "sClass": "text-center",
                 "data": "u_sex",
                 "render": function (data, type, row, meta) {

                     var content = "保密";
                     if (data == "1")
                         content = "男";
                     if (data == "2")
                         content = "女";
                     return content;
                 }

             },
             { "sClass": "text-center", "data": "u_age" },
             { "sClass": "text-center", "data": "u_registerdate" },
             {
                 "sClass": "text-center",
                 "data": "u_state",
                 "render": function (data, type, row, meta) {
                     var content = "非正常";
                     if (data == "0")
                         content = "正常";
                     if (data == "1")
                         content = "锁定";
                     return content;
                 }
             },
             {
                 "sClass": "text-center",
                 "data": "u_registerdate",
                 render: function (data, type, row, meta) {
                     
                     return "<a id='edit' title='编辑' class='glyphicon glyphicon-edit nounderline' href='javascript:Edit("+row.u_id+");'></a>";
                 }
             }

        ],
        //这个应该是重绘的回调函数
        fnDrawCallback: function () {
            var startIndex = this.api().context[0]._iDisplayStart;//获取到本页开始的条数
            this.api().column(0).nodes().each(function (cell, i) {
                //翻页序号连续
                cell.innerHTML = startIndex + i + 1;

            });
        },
    });