The inert gas radioactive isotope ⁸⁵Kr (with a half-life of 10.74 years), due to its stable physical and chemical properties, is an ideal tracer for shallow groundwater dating. In such a dating application, first the dissolved gas is extracted from groundwater in the field, then krypton is separated from the gas sample, and finally the isotopic abundance ⁸⁵Kr/Kr will be determined by an ATTA instrument. According to the atmospheric input curve of ⁸⁵Kr, the ⁸⁵Kr age of groundwater is determined. We conducted ⁸⁵Kr analysis in three wells in Zhengding County on the plains in front of the Taihang Mountains, and made a comparison with tritium (³H) method.