In order to reduce the pressure of water supply and accelerate the development of local economy and society, the authors studied the groundwater renewal ability of the Ordos Cretaceous groundwater basin, one of major water resources areas in the Ordos Basin. The dynamics of DIC in groundwater is regarded as the same as groundwater approximately. The results reflect that the groundwater renewal ability decreases with depth, the renewal rate of mediate groundwater in most part is 0.1%/a~1%/a, greater than that of deep groundwater with the renewal rate of less than 0.1%/a. The groundwater renewal ability in the northern part of the basin is greater than that in the southern part.