Abstract: A new method for extracting feature of the dynamic error of machine tool from the flatness surface is proposed.The dynamic error is identified based on the character analysis of the test result.By Daubechies wavelet,the information that contains high frequency signal and low frequency signal is decomposed from the flatness error of workpiece surface.At the same time,the wavelet transform and power spectral density analysis are combined,and the dynamic errors of machine tool from the measured flatness error of workpiece are extracted and identified.