Abstract: Through the study of the shortages and excesses in the wavelet de-nosing iterative process for γ spectrum, the relative noising signal ratio (RNSR) was put forward as the index which used to characterize the degree of de-noising, and the iterative stopping rule based on the index was established. The results of de-nosing for γ spectrum in both simulative and practical experiments indicate the rationality and validity of the RNSR and the corresponding iterative stopping rule.