Abstract: To study the hydrochemical characteristics and ion source of the typical watershed in the Hengduan mountainous region, surface water and atmospheric precipitation samples were collected in the Requ River, a tributary of the Jinsha River in eastern Tibet.Employing mathematical statistics, ion ratio, Piper diagram, and the Gibbs model, the hydrochemical characteristics of Requ River were analyzed.The influence of urban life, farming and animal husbandry activities, and mining development on the water chemistry of surface water and the primary ion sources were discussed.The results show that the pH of Requ River(mainstream and the tributary Maqu River) are 7.25～8.41,with an average value of 7.95,indicating weak alkalinity.The total dissolved solid(TDS)value ranges from 59.11 to 453.11 mg/L,with amean value of 224.94 mg/L.Ca2+ and Mg2+ are the main cations, with equivalent concentrations accounting for 66.06% and 22.07% of the total cations, respectively.HCO3- and SO42- are the main anions, accounting for 76.08% and 16.94% of the total anions, respectively.HCO3-Ca and HCO3-Ca·Mg are the primary hydrochemical types of surface water in the Requ River.Rock weathering is the main genetic mechanism of surface water ions, dominated by calcite and dolomite.