Abstract: The enrichment of fluoride in groundwater is a very complicated hydrogeochemical process， and has a close relation with geological environment. To find out the distribution and formation conditions of highfluorine groundwater， systematic analysis work from several angles， such as strata， weather， terrain and landform，hydrogeology and hydrochemistry， etc. ， was made by survey of environmental geology and test of water sample. The main distribution areas of highfluorine groundwater in this area were proved up. The formation mechanism of highfluorine groundwater was analyzed according to a large number of the groundwater chemical analysis data. The results showed that one of the most important reasons caused the formation of high fluoride water is fluorine ions in rock and soil through eluviation into groundwater. The results provide a scientific basis for the prevention of drinking water type fluorosis and the occurrence of endemic fluorosis.

Key words: formation mechanism, fluorine, groundwater, systematic analysis, endemic fluorosis