Abstract: The 36CI/CI ratios of The groundwater from Baoding and Cangzhou, Hebei Province have been measured by using the tandem accelerator mass spectrometry. It is concluded that the 36CI ages of the groundwater of the fourth group(Q,) near the mountain and the second-third(Q3-Q,) group in the east of the Baoding area are less than 100k4 that the age of the third- fourth(Q,Q1) group in the east of the Baoding area is about 314.5ha and that of the second-third group in the west of The Cangchou area is less than 100ka.