The source of periodic aliasing and its influence on the accuracy of frequency-domain forward waveform record are analyzed. When sampling interval is fixed,different sampling point N of fast Fourier transform( FFT) greatly affects the accuracy of the forward waveform record. This paper presents a method which increases the sampling point N reasonably to make the amplitude of unit impulse response after point N approaches zero value so that the degree of periodic aliasing is reduced. The performance of frequ...