在网上查了很长时间没有找到解决方法，干脆自已查看一下代码来解决吧，随是压缩过的，不过也还是好查的，工夫不负有心人，终于解决了，方法如下：
一、我们先让表格自适应宽度
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Basic DataGrid - jQuery EasyUI Demo</title>
<link rel="stylesheet" type="text/css" href="../../themes/bootstrap/easyui.css">
<link rel="stylesheet" type="text/css" href="../../themes/icon.css">
<link rel="stylesheet" type="text/css" href="../demo.css">
<script type="text/javascript" src="../../jquery.min.js"></script>
<script type="text/javascript" src="../../jquery.easyui.min.js"></script>
</head>
<body>
<h2>Basic DataGrid</h2>
<div class="demo-info">
<div class="demo-tip icon-tip"></div>
<div>The DataGrid is created from markup, no JavaScript code needed.</div>
</div>
<div style="margin:10px 0;"></div>
<table class="easyui-datagrid"
data-options="singleSelect:true,collapsible:true,url:'datagrid_data1.json',method:'get',fitColumns:'true'">
<thead>
<tr>
<th data-options="field:'itemid',300">Item ID</th>
<th data-options="field:'productid',300">Product</th>
<th data-options="field:'listprice',300,align:'right'">List Price</th>
<th data-options="field:'unitcost',300,align:'right'">Unit Cost</th>
<th data-options="field:'attr1',300">Attribute</th>
<th data-options="field:'status',300,align:'center'">Status</th>
</tr>
</thead>
</table>
<script>
$(window).resize(function () {
$('#tt').datagrid('resize');
});
</script>
</body>
</html>
二、修改jquery.easyui.min.js这个文件来解决滚动条问题
function _4bf(_4c0){
var opts=$.data(_4c0,"datagrid").options;
var dc=$.data(_4c0,"datagrid").dc;
var wrap=$.data(_4c0,"datagrid").panel;
var _4c1=wrap.width()+20;
var _4c2=wrap.height();
var view=dc.view;
var _4c3=dc.view1;
var _4c4=dc.view2;
var _4c5=_4c3.children("div.datagrid-header");
var _4c6=_4c4.children("div.datagrid-header");
var _4c7=_4c5.find("table");
var _4c8=_4c6.find("table");
view.width(_4c1);
var _4c9=_4c5.children("div.datagrid-header-inner").show();
_4c3.width(_4c9.find("table").width());
if(!opts.showHeader){
_4c9.hide();
}
可以看到我在 7001 行处加上了一个+20，这样让宽度正好覆盖滚动条