btArray[i] = Convert.ToByte(strArray[i],16);

namespace ConsoleApplication7

{

    class Program

    {

        static void Main(string[] args)

        {

            String str = "61 41";

            String[] strArray = str.Split(' ');

            byte[] btArray = new byte[strArray.Length];

            for (int i = 0; i < strArray.Length;i++ )

            {

                btArray[i] = Convert.ToByte(strArray[i],16);

                //Console.WriteLine(bt);

            }

        }

    }

}