将data-backdrop="false"选项作为属性添加到打开模式的按钮.

Add data-backdrop="false" option as attribute to the button which opens the modal.

<!-- Button trigger modal -->
<button type="button" class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal" data-backdrop="false">
  Launch demo modal
</button>

请参见模式选项