Abstract: In order to comprehensively evaluate the drift characteristics of hydrogen and oxygen isotopes in the Ordovician Karst groundwater under coal mining, this paper collects 27 samples from different runoff areas in Fengfeng mine area, analyzes the drift characteristics of D and ¹⁸O isotopes and clarifies its drift process.The results show that in the south runoff areas, the composition of hydrogen and oxygen isotopes no drift with background feature after strongly coal mining; in the eastern runoff area, the isotope D drift remarkable, the drift rate 57.14%, and simultaneously some samples D and ¹⁸O drifted together; in the north runoff area, the isotope D and ¹⁸O drift obvious, the drift rate 27.27%; the isotope D drift is related to the water-rock reaction between Ordovician Karst groundwater and silicate minerals, accompanies with the D drift equilibrium reaction; the isotope ¹⁸O drift is related to the water-rock reaction between Ordovician Karst groundwater and carbonate minerals, accompanies with the ¹⁸O drift equilibrium reaction; the isotope D and ¹⁸O drift are related to the water-rock reaction between Ordovician Karst groudwater and carbonate and silicate water-rock reactions.