The monitoring about key components of large wind turbine is important, especially blade. Damages in the material of blade in large wind turbine will cause strain and thus can produce acoustic emission. And this study is presently a new research area in china. This paper refers to the preliminary exploration of common fracture characteristic. Acoustic emission can be used to identify and diagnose the damage. Analyzing the acoustic emission characteristics of the damage in the wind turbine system is emphasized by the experiment. At first, the acoustic emission signals of two different damages and vibration signal of those are compared and analyzed to demonstrate the superiority of the time domain of acoustic emission signals based method for the damage identification. Then, the wavelet is introduced and its characteristics are illustrated. Finally, the wavelet is used to analyze and discuss the time-frequency features of the damage acoustic emission. Some frequency band of wavelets is recomposed, and the results can efficiently extract the features of acoustic emission signal and identify the damage. It offers a valuable reference to monitor the damage about blade of large wind turbine.