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="DS3231.jpg|311" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="首页" />
      <page pageid="12" ns="0" title="Wiki语法" />
      <page pageid="13" ns="0" title="Arduino之入门篇" />
      <page pageid="37" ns="0" title="BlueBird UNO SMD V3 控制板" />
      <page pageid="151" ns="0" title="温湿度传感器 - DHT11" />
      <page pageid="180" ns="0" title="温湿度传感器 - DHT22" />
      <page pageid="313" ns="0" title="RTC 1307" />
    </pages>
  </query>
</api>