Abstract: The chemical composition of groundwater in the upper reaches of Xin'an River Basin is complex. Water-rock interactions such as dissolution, precipitation and adsorption between water and water-bearing medium play an important role in controlling the formation and evolution of complex groundwater components. In this paper, mathematical statistics, principal component and cluster analysis, Gibbs model, silicic acid balance, proportion coefficient of major ions and other methods are used to study the hydrochemistry characteristics and hydrogeochemical process of the groundwater in the upper reaches of Xin'an River Basin, also analyzed the sources of hydrochemical components. The results show that the cations in groundwater in the study area are mainly Ca²⁺and Na⁺, the anions are mainly HCO^-₃, with a small amount of Cl^-and SO^2-₄. The main hydrochemical types of groundwater are HCO₃-Ca, HCO₃-Na·Ca and HCO₃-Ca·Mg. The hydrochemical components of groundwater are mainly derived from the weathering and dissolution of carbonate and silicate minerals, followed by the weathering dissolution of evaporite. The water chemical characteristics of groundwater are affected by the leaching of groundwater, the cation alternating adsorption and human activities.