Based on the predictive fuzzy control design of grey model, this paper analyses the dynamic output response of great inertia system, and proposes a hybrid contorl method, which is combined with the adaptive regulator of grey model and fuzzy variable step method. The method overcomes the deficiency of traditional predictive PID and grey prediction control, and obtains a rapid system response index without overshoot. The simulation results shows a remarkable effect and good optimal control function to great inertia system.