Abstract: Nuclear magnetic resonance (NMR) technique is the only one geophysical new method of directly detecting underground water so far. Because the high sensitivity of this method, it is very sensitive to electromagnetic noise also. In order to improve the ratio of signal to noise (S/N ratio) and this new method’s effect of detecting water, we should eliminate the noise contained in the received signal. This paper introduces a way to improve S/N ratio of the NMRS by wavelet analysis and analyzes the processed results from the cases in Xin Zhou and Wang jiawan investigation areas, finally,demonstrates the availability to use this method in practice.