You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="DPI.png|98894" />
  </query-continue>
  <query>
    <pages>
      <page pageid="25" ns="0" title="表头字段自定义" />
      <page pageid="98902" ns="0" title="极速版插件无法安装的解决方法" />
      <page pageid="98906" ns="0" title="Word和WPS插件无法安装解决方法集合" />
      <page pageid="99104" ns="0" title="WPS安装极速版插件教程" />
      <page pageid="99222" ns="0" title="WPS如何安装极速版插件" />
    </pages>
  </query>
</api>