Edit in JSFiddle

<div class="test test-1">
    <div class="inner">
        <div class="child">
            Child
        </div>
    </div>
</div>
<div class="test test-2">
</div>

.test {
    width: 100px;
    height: 100px;
}

.test-1 {
    position: relative;
    background: #f20;
}

.inner {
    width: 80px;
    height: 80px;
    transform: scale(1); /*此处会产生新的stacking context*/
    background: green;
}

.child {
    position: absolute;
    bottom: 15px;
    color: #fff;
    font-size: 30px;
    z-index: 1000;
}

.test-2 {
    position: relative;
    margin-top: -50px;
    background: #000;
}