Abstract: Objective Geothermal energy exploitation is identified as a vital way to achieve the goals of peak carbon dioxide emissions and carbon neutrality. The Moxi fault, located in the southern segment of the Xianshuihe fault zone in western Sichuan, boasts abundant geothermal resources, serving as a significant area for subsequent geothermal energy exploitation. Methods This study investigated the hydrogeochemistry of the Wandong geothermal area along the Moxi fault, analyzed the water-rock interaction process in the area based on the hydrochemical correlation, and calculated the reservoir temperatures and the mixing ratios of cold and hot water using geothermometers and the silica-enthalpy mixing model. Furthermore, this study investigated the recharge sources and elevations of geothermal water based on hydrogen and oxygen isotopes. Results and Conclusions Key findings are as follows: (1) Geothermal water along the Moxi fault exhibits hydrochemical types of HCO₃·Cl-Na and HCO₃·SO₄-Ca·Mg. The hydrochemical composition of geothermal water is subjected principally to water-rock interactions (i.e., the dissolution of calcite in Devonian marbles). Besides, the HCO₃·Cl-Na geothermal water is further affected by the mixing of magmatic water and the CO₂ degasification in the deep part of the Moxi fault. This type of geothermal water displays relatively high reservoir temperatures ranging from 159.16 ℃ to 228.57 ℃ and large circulation depths along the Moxi fault. In contrast, the HCO₃·SO₄-Ca·Mg geothermal water exhibits relatively low temperatures varying between 111.02 ℃ and 138.04 ℃ and small circulation depths along the Caoke fault, a secondary structure. (2) The geothermal water is recharged by meteoric water and deep magmatic water. Its recharge area resides in the Gongga Mountain in the western Wandong geothermal area, with recharge elevations ranging from 2382 m to 2981 m. Two genetic modes of geothermal water in the Wandong geothermal area were identified, manifesting significantly different hydrochemical characteristics and reservoir temperatures. This study will provide a more specific theoretical basis for geothermal energy exploitation in the area.