Abstract: Aiming at the flow control of hydraulic transformer, the fractional order proportion, integration and differentiation (FOPID) controller is proposed to control the position of the value plate.To optimally determine the parameters of the FOPID controller, a novel multi-objective-based parameter tuning strategy considering time domain and frequency domain requirements of the servo system is proposed.A type of self-adapting differential evolution algorithm is employed to obtain the parameters.Finally, the proposed method is numerically simulated.The time domain analysis results show that this control strategy is obviously superior to the conventional PID, FLC, and fuzzy-PID control strategy.Meanwhile, the frequency domain analysis results show that the servo system is of high robustness and can remain in the steady state.The simulation results show that the FOPID controller and the corresponding parameter turning strategy are efficient and of high performances for the position control of the value plant.