Hi vinu@asp,

Refer the below link.

Access value of HiddenField in static WebMethod in ASP.Net

Or You can declare a static variable and then assign querystring to that variable and access in side static method like below.

public static string name { get; set; }
protected void Page_Load(object sender, EventArgs e)
{
    name = Request.QueryString["Name"];
}

[System.Web.Services.WebMethod]
public static string GetCurrentTime()
{
    return "Hello " + name + Environment.NewLine + "The Current Time is: " + DateTime.Now.ToString();
}