Abstract:The pilot site for high-level radioactive waste repository in China is located in Beishan granite body of Gansu Province. Test borehole No.3(BS03) is seated in the area belonging to ground run-off zone of the regional groundwater system. The borehole is drilled specially for site evaluation. A group of depth-specific groundwater samples have been obtained for the first time from three different depth levels,i.e. 144.00–156.77,208.00–238.00,430.51–445.72 m in the borehole using a double-packer down-hole sampling and testing system. Stable isotopes d2H and d18O of the groundwater samples indicate that the recharge of the groundwater mainly comes from local precipitation. It is different from the earlier oppinion that the recharge of the groundwater comes from Qilian Mountains. 3H and CFCs contents show that the age of the groundwater at the interested depths is at least 60 years.