Abstract: In the site characterization study for high-level radioactive waste repository, the hydrogeological groundwater feature is one of the most important evaluation factors. Groundwater formation is the principal hydrogeological problem. Based on the synthetic analysis of hydrogeology, groundwater chemistry, isotopes, CFC and dynamic characteristics of water table data, the groundwater formation in Beishan preselected area of high-level radioactive waste disposal repository is discussed. The research results show that the groundwater in Beishan area is mainly phreatic water distributed in the joints and fratures of metamorphic, magmatic, clastic and carbonate rocks. The groundwater chemical components in the area possess horizontal zonation and the dynamic type mainly belongs to infiltration-evaporation-runoff type. These results in combination with groundwater isotopic and CFC data indicate that the groundwater in this area was originated mainly from the infiltration of local precipitation. The shallow groundwater is mainly recharged by modern and local precipitation, and the deep groundwater might be originated from infiltration recharge of ancient precipitation.