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="Maillard_reaction_asparagin.png|115" />
  </query-continue>
  <query>
    <pages>
      <page pageid="10" ns="0" title="蛋白质" />
      <page pageid="13" ns="0" title="脂类" />
      <page pageid="14" ns="0" title="碳水化合物" />
      <page pageid="109" ns="0" title="苯并（a）芘" />
      <page pageid="115" ns="0" title="美拉德反应" />
      <page pageid="125" ns="0" title="多糖" />
      <page pageid="172" ns="0" title="维生素D" />
    </pages>
  </query>
</api>