我有試著使用 background-size:cover;但是他的畫質直接爛掉:)
照片是1200*960

CSS

        .body1{
            width: 100%;
            height: 960px;
            position: relative;
            background-image: url("img/background.jpg");
            background-attachment: fixed; /* 固定圖像 */
            background-repeat: no-repeat;
            background-position: center center;
            z-index: -9999;
        }
        .body2{
            width: 100%;
            height: 500px;
            background-color: #fff;
            box-shadow: 10px 10px 100px hsla(240, 40%, 15%);
            position: relative;
            right: 0;
            top: 0;
        }
        .body3{
            width: 100%;
            height: 1000px;
            position: absolute;
            background-image: url("img/background-1.jpg");
            background-attachment: fixed; /* 固定圖像 */
            background-repeat: no-repeat;
            background-position: center center;
            z-index: -9999;
        }

HTML

    <div class="body1"></div>
    <div class="body2">
        <div class="body3">

        </div>
    </div>

再麻煩各位大大幫我解惑了QQ