頁面程式碼

div中 class="layui-form"  和  lay-filter="selFilter" 必需加上

<div class="layui-col-xs6" >
    <label class="layui-form-label">有效證件</label>
        <div class="layui-input-block layui-form" lay-filter="selFilter">
        <select id="reaCredential" name="reaCredential">
            <option value="1">學生證</option>
            <option value="2">身份證</option>
            <option value="3">軍人證</option>
            <option value="4">老年證</option>
        </select>
    </div>
</div>
 

ajax回撥函式中的程式碼

//下拉框賦值 
$("#reaCredential").val(data[0].reaCredential);
//渲染
form.render('select','selFilter');