Abstract: Based on the survey, data collection and analysis of water resources in Bangong Lake Basin, the hydrochemical characteristics and main controlling factors of the area are studied through mathematical statistics and hydrochemical analysis. The results show that the HCO₃-Ca type water is dominated in river, Cl·SO₄-Na·Mg type water in lake and HCO₃-Ca·Mg type water in groundwater in terms of hydrochemical types. The formation of river water and groundwater is mainly controlled by carbonate rocks and silicate rocks, and the lake water by evaporation-crystallization. The Na⁺, Cl^- and K⁺ in lake water are derived from precipitation, evaporite dissolution and dissolution of other potassium-sodium minerals, while those in river water and groundwater mainly come from evaporite dissolution. The Ca²⁺, Mg²⁺ and SO₄^2- in all water bodies are from the dissolution of carbonate rock minerals and gypsum, among which the Ca²⁺ and Mg²⁺ in river water and groundwater mainly originate from the dissolution of carbonate rocks. There is ion exchange action of Na⁺ and K⁺ in groundwater with Ca²⁺ and Mg²⁺ in aquifer or soil.