Abstract: Objective The geothermal system in Tianshui area, Gansu, China is characterized by strong tectonic activities and complex heat source mechanisms, thus limiting the development and utilization of geothermal resources. Understanding and grasping the causes of geothermal fluids and revealing the mechanism of their transport and evolution are of great significance to the rational utilization of geothermal resources in Tianshui area. Methods In this study, water chemistry and isotopic (δ²H, δ¹⁸O, δ¹³C, δ¹⁴C, δ³⁴S, δ¹¹B, ³He/⁴He) characterization methods were used to investigate the genesis of the uplifted mountain-type geothermal system in the Tianshui area. Results The results show that the geothermal fluids are recharged by atmospheric precipitation without obvious “oxygen drift” phenomenon, and the recharge elevation is 1645.69~2414.99 m. The δ¹³C value of CO₂ in equilibrium with HCO₃^- is -19.43‰~-10.96‰, which is in the range of δ¹³C of the sedimentary organic matter, and the calibrated age of the geothermal fluids is 0.46~23.07 ka, and the calculated ages of the geothermal fluids in Qingshui and Jieting are small, which may be mixed with shallow groundwater. The calibrated ages of the geothermal fluids are 0.46~23.07 ka, and the calculated ages of the geothermal fluids in Qingshui and Jieting are small, which may be mixed with shallow groundwater. δ³⁴S and δ¹¹B isotope values are 7.5‰~11.4‰ and -7.77‰~31.17‰, respectively, and sulfur and boron are mainly originated from leaching of geothermal fluids to the surrounding rocks in the process of deep circulation. 5 geothermal fluids analyzed by He isotope analysis The He isotope analysis of geothermal fluids at five locations shows that the R/Ra ratio is less than 1, which is mainly a characteristic of crustal source. Conclusions The isotopic distribution of geothermal fluids in Tianshui area is mainly characterized by shell-source features, with little shell-mantle connectivity, and the shell-source heat flow is the main contributor to the geothermal heat flow value. Tianshui area has high geothermal heat flow value and rich low temperature geothermal resources, but the exploitation potential is limited due to the difficulty of exploitation. It is recommended to diversify the utilization of developed geothermal fields, and at the same time to strengthen the degree of comprehensive research and geothermal exploration, so as to scientifically and reasonably develop and utilize the geothermal resources.