A HWPT-ZFFT (harmonic wavelet packet transform and zoom fast Fourier transform) method is proposed for spectrum zoom, targeted for a spectrum that contains three or more intense frequency components. When the signals are orthogonally decomposed into different frequency bands with no redundancy or leakage, they perform better using the box-like spectrum instead of the tradition low-pass and band-pass filter in complex modulation ZFFT. First, the HWPT method is employed to filter the intense components, shift the center frequency to zero, and resample. Then, the frequency, amplitude and phase after zoom are obtained by FFT in order to calculate the holospectrum. Finally, rich fault characteristics are obtained under higher frequency. The effectiveness of this method is demonstrated through simulation and multi-span rotor system experimental results.