Aiming at the problem of abnormal operation of the hydraulic system of the shipborne loader, the model of the hydraulic system was established in AMESim, and the cylinder displacement under different faults was simulated when the fuel leakage and the system pressure were low. The influence of load disturbance on the working of vertical conveying motor was studied in detail. The method of determining the specific position of the vertical conveyor was proposed by measuring the rotational speed of the motor. The displacement curve was obtained. The analysis results provide basis for loader condition monitoring and hydraulic system fault Diagnosis.