A offroad vehicle was researched.By the foundation of an AMESim model of offroad vehicles’ hydraulic driving system, the simulation and analysis of every module's dynamic functions in hydraulic driving system were made, and the comparison was adopted between the results of simulation and the parameters of the samples provided by manufactures. The result shows that the simulation results of the main hydraulic elements are by the large identical with the results during their actual working process, every hydraulic elements' models can be used to demonstrate the practical working process, and a solid foundation was made for the further function simulation in hydraulic driving system.