Abstract: Cambrian and Ordovician carbonate aquifers are widely distributed in North China, characterized by abundant water, high water temperatures, and easy reinjection. It is a preferred choice for the development and utilization of middle and deep geothermal resources in China. Previous research has primarily focused on the permeability, water abundance, and hydrochemical characteristics of Cambrian and Ordovician aquifers, however, the genesis of their geothermal water remains unclear, which limits the evaluation and development of these geothermal water resources. By testing and analyzing the primary ions and environmental isotopes (^34\mathrmS_\mathrmSO_4 , ^18\mathrmO_\mathrmH_2O , ^2\mathrmH_\mathrmH_2O , ¹³C_DIC, ¹⁴C_DIC) of 32 surface hydrological boreholes and underground water outlets in this area, the hydrogeochemical and geothermal characteristics of Cambrian and Ordovician carbonate aquifer groundwater in Huainan Coalfield on southern edge of North China were explored and revealed. The results show that: the carbonate outcrop area in the southern part of Huainan Coalfield is a groundwater recharge area with low water temperature (18.1−23.2 ℃), low TDS (0.28−0.49 g/L), hydrochemical type of HCO₃-Ca; The underground water runoff and discharge area in the central concealed zone has high water temperature (30.6−50.7 ℃), high TDS (1.93−3.06 g/L), a hydrochemical type of Cl-Na. The formation process of geothermal water in the central part of the research area is mainly dominated by the dissolution of evaporite rocks (rock salt and gypsum, hard gypsum) and cation exchange, followed by the combined effects of carbonate dissolution, dedolomitization, and microbial activity. The geothermal water in the study area mainly comes from the infiltration and recharge of ancient atmospheric precipitation, with a corrected age of 31.08-36.83 ka (average is 34.14 ka), corresponding to Late Pleistocene. The silica temperature scale shows that the temperature of karst thermal reservoirs in the area is 59.8−80.1 ℃ (average is 68.1 ℃), and the circulation depth of geothermal water is 1 559.7−2 273.8 m (average is 1 851.8 m). Based on the above research results, a conceptual model for the evolution of the geothermal water cycle in Cambrian and Ordovician carbonate aquifer of Huainan Coalfield was established. Driven by terrain and gravity, atmospheric precipitation in the southern outcrop area infiltrates downwards through channels such as fractures and faults. It continuously heats up deep underground to form geothermal water. During this process, groundwater interacts with carbonate rocks containing evaporite minerals, resulting in high-sodium and high-sulfate geothermal water, which ultimately discharges outward through overflow, underground drilling, and water outlet points.