Abstract:By introducing the modified coefficient of spectral magnitude, the improved harmonic wavelet packet transform is proposed. The improved harmonic wavelet packet transform makes the subband of signal maintains the spectral magnitude after the decomposition. So, the improved harmonic wavelet packet transform can extract exactly the amplitude and frequency of fault modulation signal and conveniences the fault diagnosis of mechanism. The simulation and fault signal analysis of bearing not only show that harmonic wavelet packet possesses perfect band-pass filter characteristic and excellent ability to detect weak signal, but also show that the improved harmonic wavelet packet transform authentically makes the subband of signal maintains the spectral magnitude after the decomposition and has some application value in fault diagnosis.