Use align and halign properties to set the alignment of the columns and their header.
<table class="easyui-datagrid" title="Aligning Columns in DataGrid" style="width:700px;height:250px"
data-options="
singleSelect:true,
collapsible:true,
url:'examples/datagrid/datagrid_data1.json',
method:'get'
">
<thead>
<tr>
<th data-options="field:'itemid',width:80,halign:'center'">Item ID</th>
<th data-options="field:'productid',width:100,halign:'center'">Product</th>
<th data-options="field:'listprice',width:80,align:'right',halign:'center'">List Price</th>
<th data-options="field:'unitcost',width:80,align:'right',halign:'center'">Unit Cost</th>
<th data-options="field:'attr1',width:250,halign:'center'">Attribute</th>
<th data-options="field:'status',width:60,align:'center',halign:'center'">Status</th>
</tr>
</thead>
</table>