<p>An investigation into the genesis mechanism of the geothermal system within the Dabie orogen was conducted by analyzing the hydrochemical and isotopic compositions of geothermal and cold waters along its eastern margin. The objective was to elucidate the evolution process of geothermal fluids in this region. The research focuses on the differences in hydrochemical types between geothermal water (35.70–66&#xa0;°C) and cold water (SO₄–Na·Ca, HCO₃·SO₄–Na vs. HCO₃–Ca) and uses ion ratio coefficients and concentrations of trace elements (Sr, Si, F) in the Dabie orogenic belt, China, to confirm that water–rock interaction is the dominant controlling factor. The estimated temperature of the geothermal reservoir ranges from 100.85 to 116.80&#xa0;°C (average 110.41&#xa0;°C), indicating that the mixing of cold water during ascent has not reached equilibrium. The isotopic values of δD and δ¹⁸O indicate that the geothermal water originates from meteoric water recharge, while ³H reveals the mixing of modern and ancient waters. The results show that geothermal water is recharged by precipitation in high-topography areas, infiltrates into the basement along fault zones for heating, and then rises under the action of thermal convection, forming geothermal anomalies or hot springs. By constructing a conceptual model of the genesis of the geothermal system in the Dabie orogen, this study quantitatively reveals the circulation path of geothermal fluids and the characteristics of the thermal reservoir, providing a scientific basis for the evaluation and sustainable development of regional geothermal resources.</p>