添加一个新的非绑定列，使用CustomColumnDisplayText事件来分配序号给该列

<dx:GridViewDataTextColumn Caption="序号" UnboundType="String" VisibleIndex="0"></dx:GridViewDataTextColumn>

 protected void ASPxGridView1_CustomColumnDisplayText(object sender, DevExpress.Web.ASPxGridView.ASPxGridViewColumnDisplayTextEventArgs e)
 {
  if (e.Column.Caption == "序号")
  {
   e.DisplayText = (e.VisibleRowIndex + 1).ToString();
  }
 }

ASPxGridView-为每行添加序号