The power system is characterized by oscillation in machine rotor angle and speed during and after the fault cases. Therefore, power system stabilizer (PSS) should be used for damping the power system oscillations. Modern optimization techniques have been applied to design (PSS) in recent years. In this paper, Differential Evolution technique (DE) isproposed as a modern technique to search for optimal controller parameters of PSS in Single Machine Infinite Bus (SMIB) system, by minimizing the deviation in the oscillatory rotor speed of the generator. Thistechnique is applied at specific operating point and at multiple operating points. Simulink &MATLAB environmentare used to find the optimal design which is compared to other techniques such as Genetic Algorithm (GA).