function set_select_checked(selectId, checkValue){  
    var select = document.getElementById(selectId);  

    for (var i = 0; i < select.options.length; i++){  
        if (select.options[i].value == checkValue){  
            select.options[i].selected = true;  
            break;  
        }  
    }  
}

// 设置select选中该班组
set_select_checked('selectId', checkValue);