Abstract: Analysis were conducted on acoustic emission monitoring of water pressure test for composite material type Ⅲ gas cylinders with prefabricated defects, addressing the problem of different and difficult to distinguish typical damage signal characteristics of composite material gas cylinders. Firstly, the damage stages of composite material type Ⅲ gas cylinders were divided and typical damage signals were extracted. Taking the extracted damage signal as the object, the range of acoustic emission characteristic parameters was statistically analyzed; By using continuous wavelet transform and wavelet packet decomposition, a histogram of the energy distribution of wavelet packets was drawn, and the characteristic parameters P₁ of multi frequency band energy proportion P₂ was defined, the proportion of S_K frequency band for matrix cracking signal and S_D frequency band for fiber fracture signal were analyzed. Experimental results showed that the distribution pattern of wavelet packet energy spectrum could better characterize the damage type of composite material type Ⅲ gas cylinders. When the signal satisfied P₁>0.73 and P₂<0.10, the damage signal was S_K signal. When the damage signal satisfied P₁<0.27 and P₂>0.42, the damage signal was an S_D signal. The results could provide certain reference value for the safety inspection of composite gas cylinders.