<div class="input-group">
<input type="text" class="form-control">
<div class="input-group-btn">
<button class="btn btn-default" type="button">按钮A
<button class="btn btn-default dropdown-toggle" type="button" data-toggle="dropdown">
<span class="caret">

  <ul class="dropdown-menu"&gt;
    <li>1</li>
    <li>2</li>
    <li>3</li>
  </ul>
</div>