1.设置style：

1 <style>
2  .modal-header {
3     cursor: move;
4 }
5 </style>

2.添加下列代码：

 1 <script>
 2     $(".modal-header").on("mousedown", function(mousedownEvt) {
 3         var $draggable = $(this);
 4         var x = mousedownEvt.pageX - $draggable.offset().left,
 5         y = mousedownEvt.pageY - $draggable.offset().top;
 6         $("body").on("mousemove.draggable", function(mousemoveEvt) {
 7             $draggable.closest(".modal-dialog").offset({
 8                 "left": mousemoveEvt.pageX - x,
 9                 "top": mousemoveEvt.pageY - y
10             });
11         });
12         $("body").one("mouseup", function() {
13             $("body").off("mousemove.draggable");
14         });
15         $draggable.closest(".modal").one("bs.modal.hide", function() {
16             $("body").off("mousemove.draggable");
17         });
18     });
19 </script>

 3.对于第一步，也可通过script来设置：

1 $(".modal-header").css("cursor", "move");