Abstract: The hydrochemical types and origins of underground waters collected from 15 seismic monitoring stations in Liaoning Province are discussed based on the isotope ratios of hydrogen and oxygen as well as ion concentrations. δD and δ¹⁸O values of underground water ranged from −82.5‰ to −54.4‰ and from −11.4 ‰ to −7.3‰, respectively, which indicates that the waters had a meteoric origin. Granite is widely distributed in the studied area. The cold spring waters were the type of Ca-SO₄·HCO₃ and Ca-HCO₃·SO₄, while the hot spring waters from fractured granite were mainly type of Na-HCO₃·SO₄ due to the dissolution of silicate minerals. The water samples with moderate temperature in the western and middle parts of Liaoning Province were the type of Na·Ca-HCO₃, resulting from dissolution of silicate minerals and carbonate. The concentration of F ⁻ is positively correlated with temperature, pH, concentrations of Na^＋ and HCO₃ ⁻, indicating reaction between the granite and the fluids enriched in CO₂ .