html:

<table style="width: 800px;height: 300px;border: 1px dashed #ccc;">
        <tr>
            <th>Header</th>
            <th>Header</th>
            <th>Header</th>
            <th>Header</th>
            <th>Header</th>
            <th>Header</th>
            <th>Header</th>
            <th>Header</th>
            <th>Header</th>
        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>

        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>3</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>

        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>3</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>6</td>
            <td>Data</td>

        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>3</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>

        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>3</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>3</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>3</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>8</td>
            <td>Data</td>
        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>8</td>
            <td>Data</td>
        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>4</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>8</td>
            <td>Data</td>
        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>4</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>8</td>
            <td>Data</td>
        </tr>
        <tr>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
            <td>Data</td>
        </tr>
    </table>

css:

table {
    border-collapse: collapse ;
}

th,
td {
    border: 1px solid #333;
    padding: 10px 20px;
}

js:

    $.fn.extend({
        //表格合并单元格，colIdx要合并的列序号，从0开始
        "rowspan": function (colIdx) {
            return this.each(function () {
                var that;
                $('tr', this).each(function (row) {
                    $('td:eq(' + colIdx + ')', this).filter(':visible').each(function (
                    col) {
                        if (that != null && $(this).html() == $(that).html()) {
                            rowspan = $(that).attr("rowSpan");
                            if (rowspan == undefined) {
                                $(that).attr("rowSpan", 1);
                                rowspan = $(that).attr("rowSpan");
                            }
                            rowspan = Number(rowspan) + 1;
                            $(that).attr("rowSpan", rowspan);
                            $(this).hide();
                        } else {
                            that = this;
                        }
                    });
                });
            });
        }
    });

调用：
$(“table”).rowspan(2); //第三列合并
$(“table”).rowspan(4); //第五列合并
$(“table”).rowspan(7); //第八列合并

参考地址https://www.mybj123.com/550.html