The hydraulic shift buffer system is the core system of the vehicle to reduce the shift shock and improve the shift quality. The failure of shift, shift shock, and serious local heating of the system are closely related to the abnormal state of the hydraulic shift buffer system. Based on the theoretical analysis of the hydraulic shift buffer system, the AMESim simulation software was used to model the system, and the simulation results were compared with the calculation data of the mathematical model and the data curves of the bedstand to verify the feasibility of the simulation model. The fault simulation analysis of the system was carried out by typical fault factors such as injection orifice blockage, valve core stuck, spring fatigue aging and so on. The quantitative influence results of the front end blockage of the shift buffer system, the displacement of the buffer valve core, and the spring stiffness of the pressure-holding valve on the buffer oil pressure characteristics were obtained, and the specific fault phenomena were analyzed combined with the shift oil pressure curve.