Among the various parts of the integrated gear box,the hydraulic gear shift buffering system plays the key role in the quality control of the gear shifting.Typical faults such as hock,failure,transmission efficiency decrease and abnormal temperature raise are directly correlated with the hydraulic gear shift buffering system.Based on the analysis of its construction,working principle and mathematical model,AEMSim simulation software was used to establish the simulation model of the system,and the model was verified by real vehicle test data.The typical faults mechanism such as valve spool stuck,throttle block and spring fatigue and theirs influence on the pressure characteristics of the gear shift and their influence on the shift pressure characteristics were simulated and analyzed,and the quantitative relationship between different fault mechanisms and fault characteristics was obtained.The simulation results can be used as the data support for intelligent fault diagnosis and identification of the complex mechanical-hydraulic systems such as integrated gear box.