The structural integrity of landing gear doors affects the safety of aircraft during takeoff and landing. In this paper, a method of indirectly monitoring the structural health of the landing gear door by using the strain of the door link is proposed. Firstly, a strain gauge is pasted on the landing gear outer door link of a certain type of transport aircraft to qualitatively analyze the aerodynamic force of the landing gear door during retraction and retraction; Then, the time-frequency analysis and frequency spectrum analysis of the connecting rod strain data are carried out by using the wavelet change and Fourier change to obtain the vibration response frequency of the outer door of the landing gear. The vibration response frequency is taken as the vulnerable detection value, and the evolution of the structural damage of the door is judged according to its change trend, and compared with the natural frequency of the door to analyze the cause of the structural damage; Finally, the airborne test system and monitoring system are used to realize the health monitoring of landing gear door structure during flight. The results show that this method is reliable and effective, which can detect the structural damage of landing gear door in advance, and has the value of popularization and application.