<div id="container">
 <a data-toggle="modal" href="#myModal" rel="external nofollow" class="btn btn-primary">弹出第一层模态框</a>
 <!-- 第一层模态框 -->
 <div class="modal fade" id="myModal">
   <div class="modal-dialog modal-lg">
     <div class="modal-content">
       <div class="modal-header">
         <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
           <h4 class="modal-title">第一层模态框</h4>
       </div>
       <div class="container"></div>
       <div class="modal-body">
       <p>第一层模态框</p>
       <br> 
       <a data-toggle="modal" href="#myModal2" rel="external nofollow" class="btn btn-primary">弹出第二层模态框</a>
       </div>
       <div class="modal-footer">  <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-dismiss="modal" class="btn">关闭</a>
         <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="btn btn-primary">保存</a>
       </div>
     </div>
   </div>
 </div>
 <!-- 第二层模态框 -->
 <div class="modal fade rotate" id="myModal2">
   <div class="modal-dialog">
     <div class="modal-content">
       <div class="modal-header">
         <button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
           <h4 class="modal-title">第二层模态框</h4>
       </div>
       <div class="container"></div>
       <div class="modal-body">
         <p>第二层模态框</p>
       </div>
       <div class="modal-footer">  
       <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" data-dismiss="modal" class="btn">关闭</a>
    <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="btn btn-primary">保存</a>
       </div>
     </div>
   </div>
 </div>
 <!-- 遮罩 -->
 <div id="cover"></div>
</div>

<style type="text/css">
 <!-- 遮罩是为了第二层模态框弹出时，可以将第一层模态框遮住 -->
 #cover {
 display: none;
 position: fixed;
 background: #000000;
 left: 0;
 top: 0;
 width: 100%;
 height: 100%;
 opacity: 0.40;
 z-index: 1
}
</style>

$(document).ready(function (){
 //第二层模态框弹出时，为其设置一个大于第一层模态框的z-index
 //使得第二层模态框可以在第一层模态框上面
 $(document).on('show.bs.modal', '#myModal2', function (event) {
 var zIndex = 1040 + (10 * $('.modal:visible').length+1);
   $(this).css('z-index', zIndex);
   //开启遮罩，遮罩的高度小于第二层模态框
   $("#cover").css('z-index',zIndex-1)
   $('#cover').css('display','block'); //显示遮罩层 
 });
 
 $('#myModal2').on('hide.bs.modal', function() {
 //第二层模态框关闭时，关闭遮罩
 $('#cover').css('display','none');
 });
});