The distribution regUlarity of radionuclides Th,U and K in strata is related to litholigic character,mineral composition, diagenetic environment and groundwater activity.On the basis Of natural gamma spectra and indoor analyses of 646 core samples from 27 deep drill holes in Sanzhao area and through database management system of natural gamma spectra,the authors succeeded in drawing Th-U intersection diagram and Th-K intersection diagram,thus finding out the relationship between natural gamma spectra and lithologic character.