The paper presents a new method for design of power system stabilizer (PSS) using discrete time power rate reaching law based sliding mode control technique. The control objective is to enhance the stability and to improve the dynamic response of a single machine infinite bus (SMIB) system, operating in different conditions. The control rules are constructed using discrete time power rate reaching law based sliding mode control. We apply this controller to design power system stabilizer for demonstrating the efficacy of the proposed approach.