Abstract: The mud-pulse signal in the wireless measurement while drilling system is disturbed by varieties of noises.This paper uses Fourier transform and wavelet transform to process the signal,and attempts to use correlation coefficient to estimate the processing result.Based on the correlation coefficient,it compares the processing result by using Butterworth,Chebychev and wavelet transform.Results show that wavelet transform is the optimal processing method.Wavelet transforming is better than Fourier transforming in processing the mud signal for de-noising,and the correlation coefficient can be used to judge the de-noising quality in the mud signal.