SOURCE

var box = document.querySelector('.container ul'),
    items	= document.querySelectorAll('li'),
    itemH = items[0].offsetHeight,
    boxH = box.offsetHeight,
    lengths = items.length,
    time = 1500,
    step = 2;

for(var i=0; i<step; i++) {
  var node = items[i].cloneNode(true);
  box.appendChild(node);
}
function run() {
  
  setTimeout(function() {
    var mt = parseInt(box.style.marginTop || 0);
    mt -= itemH * step
    box.style.transition = 'margin .5s';
    if(Math.abs(mt) >= boxH + itemH * step) {
      box.style.transition = 'initial';
    	mt = 0
    }
    box.style.marginTop = mt + 'px';
    run();
  },time)
}

run()

<div class="container">
  <ul>
    <li>1大促销...</li>
    <li>2大促销...</li>
    <li>3大促销...</li>
    <li>4大促销...</li>
    <li>5大促销...</li>
    <li>6大促销...</li>
    <li>7大促销...</li>
    <li>8大促销...</li>
  </ul>
</div>

*{padding:0;margin: 0;}
.container{
  margin:100px auto;
  width: 100px;
  height: 40px;
  overflow:hidden;
  border:1px solid #ccc;
}
li{
  list-style:none;
  height:20px;
  line-height:20px;
  text-align:center;
}