Landing gear device is an important component of aircraft with both load-bearing and maneuver ability. It undertakes an extremely important mission in the process of safe takeoff and landing of aircraft. Landing gear is a necessary support system for aircraft take-off, landing, taxiing, ground movement and parking. It is one of the main components of the aircraft. Its performance is directly related to the safety of the aircraft. This paper start with the failure phenomenon that the landing gear is not retracted during flight, combined with the working principle of landing gear retraction and retraction, establish a fault tree to analyze and troubleshoot the fault, finally, locate the fault point accurately. Through the analysis and processing method of establishing fault tree, it has certain guiding significance for relevant personnel to deeply understand the main components and function realization process of landing gear and expand the troubleshooting ideas of technicians.