Abstract: The geothermal water has excessive fluoride concentrations in the southern segment of Tanlu Fault. In order to support the scientific development and sustainable utilization of geothermal resources in the southern segment of Tanlu Fault, the authors explored the evolution mechanisms, and formation patterns of high-fluoride geothermal water, and evaluated the health risk. Eleven water samples were collected in the southern segment of TanLu Fault, and geothermal water distribution and characteristics were identified via hydrochemistry, hydrogen/oxygen isotope testing, hydrogeochemical diagrams and ion ratio analysis. Besides, the cycle process and reservoir forming condition of the fluoride-enriched geothermal water along Tanlu Fault were explored. The results show that the local groundwater is HCO₃-Ca type (acidic), while geothermal water is mostly SO₄-Na type (alkaline). The fluoride-enriched water occurs mainly in geothermal reservoirs, with the fluoride levels exceeding national standards by 2~12 times. While the groundwater fluoride levels are within limits. The geothermal water is mainly recharged by atmospheric precipitation at 1 116~1 453 m elevation, circulating at 1 259~1 534 m depth, and reservoir temperature of 106.5~119.2 ℃ (via quartz geothermometry). The fluoride-enriched geothermal water chemistry is shaped by multiple hydrogeochemical processes. Fluoride-enriched mineral weathering/dissolution is the main cause of high fluoride, while alkaline conditions and cation exchange also contribute to fluoride accumulation. Health risk assessment shows that high-fluoride geothermal water poses a greater potential risk to children than to adult women/men. The evolution mechanisms and formation patterns of high-fluoride geothermal water in the southern segment of Tanlu Fault were defined, and the causes of high fluoride and health risk differences were revealed, providing scientific basis for local geothermal resource management. The differential health impacts of high-fluoride geothermal water on different populations were emphasized and it is highly significant for ensuring local residents' water safety, particularly for children.