Abstract: Aiming at the problem of small sample size in intelligent fault diagnosis of hydraulic loading system in structural strength test, AMESim simulation software is used to build the detailed physical model of two-stage double nozzle electrohydraulic servo valve and hydraulic actuator cylinder. Then the simulation model of displacement loading hydraulic system is established. With this model and fault injection technology, the common faults of hydraulic system are simulated. The research shows that the model can effectively represent the operation characteristics of the system and obtain fault samples,which is of great significance to the research of intelligent fault diagnosis of hydraulic system.