Compared with the traditional hydraulic hybrid system, step variable hydraulic hybrid power system has the advantages of low cost, fast response and pollution resistance. However, the existing variable elements are heavy, and the control valve group has the disadvantages of insufficient through-flow capacity, large flow resistance, large leakage and reversing impact. In this study, the hydraulic components integrated by the cartridge valve group which can replace the traditional three-position four-way valve group are applied to the hydraulic hybrid power system. The AMESim simulation models of directional cartridge valve and the step variable hydraulic hybrid power system are established in this study. Through simulation analysis, it is verified that the cartridge valve integrated element can replace the traditional reversing valve to solve the defects of cumbersome components and insufficient through-flow capacity. Some important parameters of the system components are simulated and analysed. The simulation results can be used to improve the design efficiency and ensure the design quality.