#bbox{
        position: absolute;
        top: 166px;
        left: 219px;
        background: #fff;
        width: 548px;
        border: 1px solid #999;
    }
    #bbox #seach-ul{
        list-style: none;
    }
    #bbox #seach-ul li{
        height: 50px;
        line-height: 30px;
        padding-left: 10px;
    }
    #bbox #seach-ul li:hover{
        background: #e5e5e5;
        text-decoration: underline;
    }
    //body
    <div id="bbox" style="display: none;">
        <ul id="seach-ul">
        </ul>
    </div>
    //script
    $('#txt').on('keyup', function (e) {
        var text = $('#txt').val();
        var html = '';
        html += '<li>' + text + '</li>'
        $('#seach-ul').html(html);
        $('#bbox').show();

    });
    

为什么动态添加完li之后，先前的设置的样式不见了