The bending moment test used by the specimens with partial and circumferential wall thinning was carried out to obtain the AE signal. The time-frequency analysis method for the investigation of the frequency characteristics of the AE signal was applied. The results of the wavelet analysis were compared with those of the bending moment test for the structural integrity of tube. The result of the frequency characteristics by applying wavelet analysis method and dropping ball test was presented similarly to those of bending moment test. It is considered that this simple method with combination of dropping ball test and wavelet analysis is very useful scheme for investigating the structural integrity.