Abstract: The acoustic emission (AE) technique was used for real time monitoring the fatigue damages of one key inaccessible component(the half shaft), during its functional test of the horizontal tail for a certain plane, and it was carried out under the severe shock and vibration. Based on the analysis of simulated testing signal, the pre-processing principle of the acquired data was presented, and the signal/noise ratio was greatly enhanced. During monitoring, the methods of trend analysis and correlation analysis of AE parameters were used, they could sufficiently reflect the fatigue damages process of the component, and then the feasible acoustic emission real-time monitoring method about the aircraft key components were pointed out.