Abstract: Taking the geothermal water in Gonghe basin of Qinghai Province as the research object,the water samples were tested for the hydrochemistry and hydrogen and oxygen isotope,and the results were analyzed. The analysis results show that the main hydrochemical type of geothermal water in Gonghe area is Cl-Na type. Geothermal water is greatly affected by the superficial oxidation of shallow surface layer,and the sealing of the environment is poor. Geothermal water is supplied by rain. The geothermal heat source and water source are not the same. Geothermal water does not reach the chemical equilibrium state of water-rock reaction,The reservoir temperature of geothermal water is estimated to be the range of 37.59-108.22 ℃. The circulation depth of geothermal system is 500-2000m,which belongs to the medium temperature geothermal system.