I just think this is my variable getting data from  database 
I declare Description properties in separate class
public class Description
{
  public int DesID{set;get;}
  public string Description{
} 
C# Coding : Data
[WebMethod]    
    public static List<Description> Data()
    {
      List<Description> listDescription = new List<Description>();
      Description d1=new Description()
       {
         DesID=1,
         Description ="ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890abcdefghijklmnopqrstuvwxyz";
       };
      Description d2=new Description()
       {
         DesID=2,
         Description ="thanks for your response"
       };
    listDescription.add(d1);
    listDescription.add(d2);
    }
JSON :
 $(document).ready(function () {
            $(function () {
                $.ajax({
                    contentType: 'application/json; charset=utf-8',
                    url: 'WebForm1.aspx/Data',
                    dataType: 'json',
                    method: 'post',
                    success: function (data) {
                        for (var i = 0; i < data.d.length; i++) {
                            $('#divdisplay').append("<div>Description ID : "+ data.d[i].DesID+"<br/>Description : "+data.d[i].Description+</div>");
                        }
                    },
                    error: function (result) {
                        alert('Error');
                    }
                });
            });
Important Note :-
I already tried this below code, but it is not working
$(data.d[i].Description).val().substr(1,5); And
data.d[i].Description.val().substr(1,5)
$(data.d[i].Description).val().substring(1,5); And
data.d[i].Description.val().substr
 
    