<form id="form1" runat="server">

<ToolTips>

       <ext:ToolTip

            ID="RowTip"

            runat="server"

            Target="={GridPanel1.getView().el}" 或 Target="={GridPanel1.getView().mainBody}"

 　　　　　　Delegate=".x-grid3-td-20 "  这里是要显示tooltip的CSS，全部列都显示则是".x-grid3-cell ",这些值可以F12去查找。

　　　　　　TrackMouse="true">

 <Listeners> 

<Show Fn="showTip" /> 

</Listeners> 

</ext:ToolTip> 

</ToolTips> 

</form>

   <script type="text/javascript" language="javascript">

      var showTip = function () {

            var rowIndex = GridPanel1.view.findRowIndex(this.triggerElement),

                cellIndex = GridPanel1.view.findCellIndex(this.triggerElement),

                record = Store1.getAt(rowIndex),

                fieldName = GridPanel1.getColumnModel().getDataIndex(cellIndex),

                data = record.get("取值列名");

                this.body.dom.innerHTML = data;

        };

    </script>