In this paper, in order to ensure the safety and reliability of the aircraft conditioning system, the failure mode and effects analysis(FMEA) of the main parts of aircraft air conditioning system is carried out. The whole air conditioning is simulated by Matlab/Simulink, and the failure diagnosis criteria of the key parts of an air conditioning system are regulated. Then, the abnormal cabin temperature of the aircraft is taken as an example to demonstrate the fault tree analysis method (FTA). The results show that the failure of the turbine has the largest influence on the abnormal cabin temperature, which should be took into serious consideration when it comes to the work of design and maintenance.