在需要合併單元格的datagrid中加入onLoadSuccess事件：

onLoadSuccess: function (data) {
            //指定列進行合併操作
            $(this).datagrid("autoMergeCells", ['列名1', '列名2']);
        }

其中的autoMergeCells方法需要寫一下：

 $.extend($.fn.datagrid.methods, {
            autoMergeCells: function (jq, fields) {
                return jq.each(function () {
                    var target = $(this);
                    if (!fields) {
                        fields = target.datagrid("getColumnFields");
                    }
                    var rows = target.datagrid("getRows");
                    var i = 0,
                    j = 0,
                    temp = {};
                    for (i; i < rows.length; i++) {
                        var row = rows[i];
                        j = 0;
                        for (j; j < fields.length; j++) {
                            var field = fields[j];
                            var tf = temp[field];
                            if (!tf) {
                                tf = temp[field] = {};
                                tf[row[field]] = [i];
                            } else {
                                var tfv = tf[row[field]];
                                if (tfv) {
                                    tfv.push(i);
                                } else {
                                    tfv = tf[row[field]] = [i];
                                }
                            }
                        }
                    }

                    $.each(temp, function (field, colunm) {
                        $.each(colunm, function () {
                            var group = this;
                            if (group.length > 1) {
                                var before,after,
                                megerIndex = group[0];
                                for (var i = 0; i < group.length; i++) {
                                    before = group[i];
                                    after = group[i + 1];
                                    if (after && (after - before) == 1) {
                                        continue;
                                    }
                                    var rowspan = before - megerIndex + 1;
                                    if (rowspan > 1) {
                                        target.datagrid('mergeCells', {
                                            index: megerIndex,
                                            field: field,
                                            rowspan: rowspan
                                        });
                                    }
                                    if (after && (after - before) != 1) {
                                        megerIndex = after;
                                    }
                                }
                            }
                        });
                    });
                });
            }
        });