Abstract: As the research site of four watersheds around Jiaozhou Bay, this article investigated and took samples of groundwater and riverine water on September and October 2011 to analysis and study the distribution characteristics of ²²²Rn activities and the influence factors in the water around Jiaozhou Bay. The samples were taken by special sampling bottle from RAD7 and placed about 15 min to reach the radioactive equilibrium status. Then the activities of ²²²Rn can be measured by emanometer RAD7 and RAD-H₂O. The results show that the activities of ²²²Rn in groundwater and riverine water from the regional scale are much higher in the magmatic areas and the fault developed areas which contain higher concentration of ²³⁸U decay series. Some adjacent sampling points vary widely both in groundwater and riverine water. The activities of ²²²Rn in groundwater and riverine water around Jiaozhou Bay mainly depend on the activities of ²³⁸U decay series from the nearby soil and rocks. Other geological factors such as fault development, hydrodynamic condition, hydrogeological factors, petrological and mineralogical properties can also affect the activities of ²²²Rn to some extent. In addition, the degree of supply from the groundwater and human activity are other two important factors to the activities of ²²²Rn in riverine water.