Abstract: Acoustic emission, which was produced when the material or structure received the external force or internal force, had a complex components, including some high-frequency signal with low relative energy and some disturbance signal with low frequency. In research, only some frequency bands are thought to be interest, and needed to be analyzed. The signals with complex frequency components can be decomposed into different frequency bands by wavelet packet transformation. Then, the signals required will be extracted by frequecy and energy factor. The acoustic emission signals produced during the tensile test of steel Q235 was acquired and proceeded by wavelet transform and energy analysis. Testing results showed the capability of the denoise value of wavelet method on acoustic emission signals.