Abstract: The relation between ⁴⁰K and gross β in natural water were described systematically for the first time based on the typical radioactive data results of local groundwater and natural water in other parts of the world and auxiliary data analysis by SPSS.⁴⁰K was often the main contributor of gross β in natural water.The correlation between ⁴⁰K and gross β in natural water was statistically significant （P<0.05）,even apparently statistically significant （P<0.01） in most cases.There was well positive correlation between ⁴⁰K and gross β and abnormal value phenomena of ⁴⁰K and gross β were found by Box-plot method analysis.⁴⁰K and gross β in natural waters should be analyzed and evaluated simultaneously to obtain more accurate measured data.