The internal leakage of the hydraulic system is very trouble in aviation maintenance. The influence factors are many. The troubleshooting process is very complex. The time required is very long. AMESim was used to set up the internal leakage model for a certain type of transport airplane’s ground spoiler.The conclusion was that the common failure type of the aircraft ground spoiler was about the hydraulic system. The hydraulic simulation model was built based on AMESim.The internal leakage in cases of the actuator with different internal leakage gap, different loads, and different hydraulic pressure were analyzed. This research can provide reference for aircraft maintence person when he is in maintenance.