Forming speed is one of the key factors affecting metal forming performance. Aluminum in different forming stages need to control different extrusion speed, and withstand different extrusion load. The accuracy and stability of forming speed directly affect the quality of aluminum. Aiming to improve the stability of the forming speed under variable load, the paper established segmented model according to the forming speed and load force conditions. And the unified switching control strategy is proposed based on robust feedback linearized control. In order to improve the robustness of the system, the control law adding compensation items to the variable load disturbance is designed based on the sliding mode control. The boundary layer function is introduced instead of the symbolic function to reduce the system flutter. The proportional derivative control (PD) control, robust control and unified switching control are compared with that of simulation and experiment. The results show that proposed method not only maintains good tracking performance but also has strong robustness under external load disturbance.