Based on chemical features and isotope analyses of water from JR5 to JR9 wells in the geothermal field of Jingshan County, the authors determined the replenishment fountainhead and path of the water.Chemical change of water in JR7 well in the past 30 years has been related to mixture of hot and cool water and cooling of terrestrial heat liquid. Geochemical thermometric scales of K, Mg and silicon dioxide were chosen to estimate temperature of the geothermal reservoir, and the results of the SiO2 thermometric scale are almost consistent with the K and Mg thermometric scale, with the thermodynamic equilibrium temperature of the geothermal field being 99～108 ℃, and the depth of the thermal reservoir being 744 meters. Researches on isotope tracing indicate that the recharge source of the geothermal field is meteoric water, and the recharge height should be over 800 m. Calculation of the halflife of tritium shows that the duration of the runoff should be 40～60 years. An analysis of regional geological conditions reveals that the replenishment area of the geothermal fluid is located in Dahong Mountain area about 60 kilometers northwest of the geothermal field, and the activity and eruption of basalts have brought a mass of heat energy. In addition, Jingshan area has a deep fracture, which could provide the pathway for groundwater; the water is heated through deep circulation and then concentrated near Tangyangfan，thus forming the geothermal field.