Abstract: The Ordos Cretaceous Groundwater Basin is an important energy basin of China. The CFCS method is applied in the Ordos Cretaceous Groundwater Basin to determine the young groundwater age and the exact results have been derived. It can be concluded that the Cretaceous Groundwater Basin can be divided into local groundwater system, middle groundwater system and regional groundwater system. The cycle rate in the local groundwater system is fast and the age is about 20 years old, which increases with the depth. The cycle rates of the middle groundwater system and the regional groundwater system are relatively slow, which ages are older than 70 years, and the correct ages can be derived from other isotopes such as ¹⁴C.

Key words: Ordos Cretaceous Groundwater Basin, shallow groundwater, CFC_S, groundwater age