Please set the 'fit' to false for the datagrid component.
<div id="tt3" class="easyui-tabs" border="true" style="height:auto">
<div title="Tab1">
<div>Label 1</div>
<div>Label 2</div>
<div>Label 3</div>
</div>
<div title="Tab2">
<table id="dg" border="false" fit="false">
</table>
</div>
</div>