function addEventSimple(obj, evt, fn) {
    if (obj.addEventListener) {
        obj.addEventListener(evt, fn, false);
    } else if (obj.attachEvent) {
        obj.attachEvent('on' + evt, fn);
    }
}
addEventSimple(window, 'load', initScrolling);
var scrollingBox;
var scrollingInterval;
var reachedBottom = false;
var bottom;

function initScrolling() {
    scrollingBox = document.getElementById('xst');
    scrollingBox.style.overflow = "hidden";
    scrollingInterval = setInterval("scrolling()", 50);
    scrollingBox.onmouseover = over;
    scrollingBox.onmouseout = out;
}

function scrolling() {
    var origin = scrollingBox.scrollTop++;
    if (origin == scrollingBox.scrollTop) {
        if (!reachedBottom) {
            scrollingBox.innerHTML += scrollingBox.innerHTML;
            reachedBottom = true;
            bottom = origin;
        } else {
            scrollingBox.scrollTop = bottom;
        }
    }
}

function over() {
    clearInterval(scrollingInterval);
}

function out() {
    scrollingInterval = setInterval("scrolling()", 50);
}

演示文件下载：https://pan.baidu.com/s/1o9m9R0u
源自：http://www.jq22.com/webqd3791