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 afcontinue="DS3231.jpg|311" />
  </query-continue>
  <query>
    <allfileusages>
      <f fromid="1" ns="6" title="File:Battery.png" />
      <f fromid="37" ns="6" title="File:Bluebird正面.jpg" />
      <f fromid="13" ns="6" title="File:Board.jpg" />
      <f fromid="1" ns="6" title="File:Chassis.png" />
      <f fromid="12" ns="6" title="File:Colorlist.jpg" />
      <f fromid="151" ns="6" title="File:DHT11串口监视结果.jpg" />
      <f fromid="151" ns="6" title="File:DHT11温湿度传感器模块.jpg" />
      <f fromid="180" ns="6" title="File:DHT22温湿度传感器串口监视.png" />
      <f fromid="180" ns="6" title="File:DHT22温湿度传感器模块.jpg" />
      <f fromid="313" ns="6" title="File:DS1307串口显示结果.png" />
    </allfileusages>
  </query>
</api>