Power system dynamic performance is improved by the damping of system oscillations. Power system stabilizers are added to excitation systems to enhance the damping during low frequency oscillations. In this paper, the structure of a power system stabilizer based on PID controller for system stability enhancement is presented. The voltage regulator excitation system is assumed to be equipped with IEEE type-DC1exciter model. The application of the controller is investigated by means of simulation studies on a single machine infinite bus power system. For the system without any PSS and the system with conventional PSS (CPSS) and proportional-integral-derivative PSS (PID-PSS), the system responses for three different conditions were obtained using equations linear simulation. Eigenvalues analysis is used for comparison. The simulation results show that, the controller is effective in improving steady state and dynamic system performances regardless of the system operating conditions.