Please look at this topic:
http://www.jeasyui.com/forum/index.php?topic=5430.0or use the 'dropAccept' property to constrain the dropping nodes.
<div class="aa">
<table id="aa" class="easyui-treegrid">
...
</table>
</div>
<table id="bb" class="easyui-treegrid"
data-options="
dropAccept: '.aa tr[node-id]',
onLoadSuccess: function(row){
$(this).treegrid('enableDnd', row?row.id:null);
}
">
</table>