This paper presents PSS (Power system stabilizer) design based on optimal PID fuzzy (OPIDF), OPIDF PSS design is considered for single-machine power systems. The main motivation for this design is to stabilize or to control lowfrequency oscillation on power systems. Firstly, describing the linear PID control then to combine this PID control with logic control mechanism. Finally, Fuzzy PID parameters (Kp, Kd, KI, Kupd, Kui) are tuned by Particle Swarm Optimization to reach optimal global stability. The effectiveness of the system in enhancing the stability of the power system, is confirmed through the simulation results.