Abstract: The exploitation and utilization of geothermal resources bring good economic benefits and social value, but the unreasonable exploitation and utilization of geothermal resources could cause serious pollution to surface water and shallow groundwater.By means of hydrochemical analysis and hydrogeochemical simulation, the hydrochemical characteristics of geothermal water and its formation in the south of Langfang were analyzed.The results show:In Neogene system the main chemical types of geothermal water in the Minghuazhen group were HCO₃-Na and HCO₃·Cl-Na.The chemical types of the geothermal water in the Guantao group were mainly Cl-Na and Cl·HCO₃-Na.In this layer, the hydraulic connection is relatively good, and the main water-rock action in the geothermal water runoff area is the dissolution of sulfate and silicate minerals, and the cationic alternating adsorption.The hydrochemistry of geothermal water in bedrock fissure thermal storage is Cl-Na, the hydraulic relation of this layer is relatively weak, and the cationic alternating adsorption is the main water-rock interaction in its hydrochemical evolution.Hydrogeochemical quantitative simulation based on PHREEQC reveals that geological background, hydrogeological conditions and human activity factors jointly controlling the degree of flow field and water-rock interaction of underground hot water, which is of certain significance for studying the hydrochemical evolution mechanism of geothermal water and the dynamic characteristics of geothermal water in Langfang area.