For 4000 t large intelligent semi-solid squeeze casting machine, the simulation model of the injection hydraulic system was built, and the influences of key parameter changes on the performance of injection system were intuitively displayed by simulation analysis. The simulation results show that the accumulator is selected as the power source of the injection system, which can completely meet the requirements of process and equipment. The volume of injection accumulator has no effect on the velocity in the injection stage, but the higher the volumes is, the earlier the opening time of booster is. The volume of booster accumulator has little effect on the injection system. The higher the setting pressure of injection accumulator is, the higher the maximum injection speed can be achieved in the injection stage, and the earlier the booster opening time is. However, as the setting pressure of injection accumulator decreases, the booster cannot be realized. The setting pressure of booster accumulator has no influence on the injection stage, but the higher the setting pressure of booster accumulator is, the higher the pressure after the booster is. The parameters of injection accumulator and booster accumulator affect the performance of injection system, so it is necessary to reasonably match the hydraulic components. Thus, it can provide a basis for the design of injection control system for the subsequent squeeze casting machine.