$(document).ready(function () {
var menuYloc = $("#leftmenu").offset().top; //此ID为随着屏幕滚动div的ID
$(window).scroll(function () {
var offsetTop = menuYloc + $(window).scrollTop() + "px";
$("#leftmenu").animate({
top: offsetTop
}, {
duration: 600,
queue: false
}); //此ID为随着屏幕滚动div的ID
});
});