Geothermal energy is green and sustainable, which is crucial to achieving the "double carbon" goal. The Yinchuan Basin is a typical cold and arid region with a huge demand for heat energy. Previous research on geothermal energy in the Yinchuan Basin mainly focused on estimating the amount of geothermal resources, and there were few studies on the hydro-chemical characteristics and formation mechanism of geothermal water. Therefore, the hydro-geochemistry, hydrogen and oxygen stable isotope, radioisotope (tritium and¹⁴C) dating, and water-rock interaction simulation were used to analyze the chemical characteristics and formation and evolution mechanism of geothermal water in the Yinchuan Basin. The research results show that the hydro-chemical types of geothermal water in Yinchuan Basin are Cl-Na type and Cl·SO4-Na type. The main cation of geothermal water is Na⁺, and the main anion is Cl^-. Na⁺ comes from the dissolution of rock salt and the alternating adsorption of cations. mainly comes from the dissolution of gypsum. The elevation of the recharge area in the Yinchuan Basin ranges from 2 600 to 2 900 m, with an average recharge elevation of 2 762.44 m. The source is that the atmospheric precipitation at high altitudes in the Helan Mountain area recharges the underground hot water in the Yinchuan Basin along the faults and broken zones. The oldest age of geothermal water is 20 750 a, there is mixed water of sub-modern groundwater, and the recharge elevation is high and the distance is long.