<video id="video" width="200px" height="auto" src="videos/demo.mp4" >

    your browser does not support the video tag!

<!--当浏览器不支持html5的video标签时，做出相应的提醒。-->

</video>
<script src="http://files.cnblogs.com/files/heyiming/jquery-2.1.4.min.js"></script>

<script>

    $(document).ready(function(){

        $("#video")[0].addEventListener("loadedmetadata", function(){

            var tol_time = this.duration;//获取视频总时长

            alert(tol_time);

        });

    });

</script>