Abstract: In this paper,according to the mathematico-physical characteristics of the interference components on groundwater radon data,the optimum periodic spectrum mixed regression analysis is suggested for qantitative elimination of the nonrandom interference. The programs of this method are as follows:1)Extraction of the nonrandom components of interference factors.2)Construction of the mixed regression equation on the basis of the optimum periodic spectrum of the radon data and the nonrandom components of the interference factors,separation of nonrandom information from nonrandom interference.3)Formation of the interfarenc model with the nonrandom components of the interference factors and some periodic components of the radon data (including trend components).It is shown,by analysis of several examples,that the nonrandom interference separated from radon data with this model,has a definite physical meaning and less additional interference,and therefore has a higher resolution of anomaly than the regression analysis.