The hydroproof acoustic emission (HAE) testing, which is acoustic emission (AE) testing during hydroproof testing, has been investigated as a robust tool to evaluate the structural integrity of the pressure vessels not only considering defects existed before the hydroproof testing but also considering damages occurred during the hydroproof testing[1,2]. In the HAE testing of a filament-wound composite pressure vessel, what plays the most important role is AE signatures which are elastic waves produced by the growth of damages and propagated through the vessel in a form of very dispersive Lamb waves and finally monitored by AE sensors, since the failure behavior of the vessel is inferred from these signals[3]. Thus, there are naturally two key issues in the HAE testing; 1) determination of the optimal mode of elastic waves to be monitored during the HAE testing, and 2) processing of AE signals to predict the failure behavior of the vessel. Here, we present our efforts to develop a systematic procedure of the HAE testing for the prediction of failure behavior in composite pressure vessels, addressing these two key issues together.