Here is The Perfect Answer. I just Discovered it.
You need to create form. and put all fields which you want to send with request.
And Give that form id to jqGrid as formIds.
<form id="myForm">
<s:select label="Select a month"
headerKey="-1"
headerValue="Select Month"
list="#{'1':'Jan', '2':'Feb', '3':'Mar', '4':'Apr'}"
name="yourMonth"
value="2"
id="selectedMonth"/>
<input type="text" name="par1" value="OOOOOOO1"/>
<input type="text" name="par2" value="OOOOOOO2"/>
<input type="submit" value="Submit" onclick="myAjaxFunction();"/>
</form>
<s:url var="remoteurl" action="jsontable" >
<s:param name="par1">Kshitij</s:param>
</s:url>
<sjd:grid id="gridtable"
formIds="myForm"
caption="Customer Examples"
dataType="json"
href="%{remoteurl}"
pager="true"
gridModel="gridModel"
rowList="10,15,20"
rowNum="15"
rownumbers="true">
<sjd:gridColumn name="id" index="id" title="ID" width="200"/>
<sjd:gridColumn name="name" index="name" title="Name" sortable="true" />
<sjd:gridColumn name="country" index="country" title="Country" />
<sjd:gridColumn name="city" index="city" title="City" />
<sjd:gridColumn name="creditLimit" index="creditLimit" title="Credit Limit" />
</sjd:grid>