Highcharts 显示不了数据问

Question

  var chart;
        $(document).ready(function () {
            chart = new Highcharts.Chart({
                chart: {
                    renderTo: 'container',
                    plotBackgroundColor: null,
                    plotBorderWidth: null,
                    plotShadow: false
                },
                title: {
                    text: '图表'
                },
                tooltip: {
                    formatter: function () {
                        return '<b>' + this.point.name + '</b>: ' + this.y + ' %';
                    }
                },
                plotOptions: {
                    pie: {
                        allowPointSelect: true,
                        cursor: 'pointer',
                        dataLabels: {
                            enabled: true,
                            color: '#000000',
                            connectorColor: '#000000',
                            formatter: function () {
                                return '<b>' + this.point.name + '</b>: ' + this.y + ' %';
                            }
                        }
                    }
                },
                series: [{
                    type: 'pie',
                    name: 'Browser share',
                  //  data: [['测试', 33],['测试赛', 33]]
                     date:Json/piedata 
                }]
            });
        });
 后台 
   Json = L JSONSerializer.DtToJSON(dt); //js格式
    piedata = "  [['测试', 33],['tets', 33]]";
为什么 我把里面的 data数据源  改为后台返回的值 ，那饼图就显示不出来呢？？？ 望大神讲解。