Abstract: Due to high speed and high precision, the accuracy of detecting method of high speed rotating machine is low, and low accuracy is the biggest obstacle to status detection. A method of reducing frequency mixed in the procedure between resolvement and reconstitution of wavelet was designed in this paper. The algorithm uses Fourier transformation and inverse Fourier transformation to construct orthogonal image filter bank in the procedure of resolvement and reconstitution, so as to achieve ideal cut-off-eigenschaft in Mallat wavelet transformation, and at the end, redundant frequency can be reduced. The wavelet algorithms before and after improvement were used to analyze the actual signal. The results show that the improvement Mallat wavelet algorithm can reduce frequency mixed in the signal analysis.