Abstract <p>The Jiangnan orogenic belt is situated in the tectonic collision and convergence zone between the Yangtze Block and the Cathaysia Block. It represents a significant geological unit for the study of the tectonic evolution of South China. The region is situated at a plate convergence site, with favourable geothermal geological conditions and a plentiful supply of geothermal resources. However, the evolution process and heat source mechanism of geothermal water in the study area remain unclear, which impedes the exploration, exploitation and utilisation of deep geothermal resources and the realisation of the goal of carbon emission reduction. In this study, temperature measurements of geothermal wells and fine geotechnical thermophysical property tests were conducted. Terrestrial heat flow and heat fluxes at different depths were calculated, terrestrial heat flow characteristics of the area were identified, the blank area of terrestrial heat flow measurements was filled in, and geothermal water in the area was collected for tests and analyses of hydrochemical characteristic indexes and other aspects. In conjunction with the regional geological and tectonic background, the terrestrial heat flow and geothermal water chemistry in the study area were investigated. The source of heat and the formation mechanism of geothermal water in the study area were analysed, and the formation mode of geothermal resources in the central part of the Jiangnan orogenic belt was revealed. The results show that the measured terrestrial heat flow values of the geothermal boreholes in the study area are 79.68 and 88.31 mW/m², which are significantly higher than the average value of mainland China, indicating that there is an abundance of heat flow from the deep part of the earth to the surface in this area. The terrestrial heat flow values of the DR02 borehole show the distribution of high in the shallow part and low in the deep part, which suggests that the heat flow from the deep part of the earth in the study area is rapidly rising along the faults and then spreads in the shallow part, and it also suggests that new heat energy has been generated in shallow rock bodies. It also indicates that there is new thermal energy generation in the shallow rock body. The chemical types of geothermal water in the study area mainly include HCO₃ · SO₄–Na, HCO₃–Ca&#xa0;·&#xa0;Mg, and SO₄ · HCO₃–Na, and the water-rock interaction has not been balanced yet. The geothermal water in the study area is influenced by the infiltration of atmospheric precipitation in the process of formation, and is of terrestrial genesis. The reduction of geothermal water in the study area is not complete, and the thermal reservoir environment is poorly closed. The flow path of the geothermal water is shorter, the circulation is more efficient, the flow rate is faster, the water circulation is faster, and the degree of metamorphism is relatively shallow.</p>