Because of the limitations of traditional PID controller for servo hydraulic cylinder position control had large overshoot, low steady state accuracy, longer response time, the method of on-line parameter self tuning fuzzy PID control was proposed, and the feasibility of fuzzy PID controller based on PLC was analyzed. The control test for proportional servo cylinder of automotive leaf spring test bench was made. The results show that the fuzzy PID controller based on PLC is simple and practical. It has high control precision, good adaptability, strong anti interference ability and good robustness. So the control quality is improved, the control requirements are met.