The transfer function model of a hydraulic loading testing system for automotive steering system was built.Using the characteristic index of the integration of absolute difference-ITAE times the time as an assessment criterion,the optimal PID controller parameters were calculated with the help of Matlab.The fractional-order PID controller was designed and built by using the FOMCON tool box.The fractional order λ and μ were picked,and both factors were varied individually to see the influence to the control effects.In the range of 0~1,the factor λ has bigger influence than the factor μ.Fixing the optimal parameters of PID,the optimal fractional order factors were determined.The simulation shows the controller meets the technical requirement,and on the Bode diagram it can be seen that the system is stable.