Yan’an Formation groundwater is an important underground drinking aquifer in the Shendong mining area,and the level of its F-content directly affects the safety of drinking water and the surrounding ecological environment. However,the characteristics of F-content,spatial distribution and formation mechanism in groundwater of the Yan’an Formation in this region have received little attention. The project team systematically collected 30 groups of Yan’an Formation groundwater in August-September 2020,and explored the characteristics of F-content,spatial distribution and formation mechanism in Yan’an Formation groundwater in terms of mineral dissolution and precipitation,evaporation,cation exchange,competitive adsorption and anthropogenic pollution effects by using Piper diagram,correlation analysis,PHREEQC simulation,etc. The results showed that the concentration of F-in groundwater of the Yan’an Formation in the Shendong mining area ranged from ND to 17. 60 mg / L,with an average value of 4. 55 mg / L. Compared with the national sanitary standard for domestic drinking water (GB 5749—2006) (1. 0 mg / L),73. 3% of the samples exceeded the standard. High TDS,Cl-,HCO3-,Na+and low Ca2+and Mg2+water environment are favorable for F-enrichment,and Na-HCO3type,Na-HCO3-Cl type and Na-HCO3-SO4type are the main hydrochemical types of high fluoride water. Fluoride-bearing mineral dissolution is an important source of groundwater F-in the Yan’an Formation. The salt effect under evaporite dissolution and silicate weathering reduces the solubility of fluoride-bearing minerals and promotes the dissolution of F; cation exchange further accelerates the dissolution of fluoride-bearing minerals through sodium-calcium transfer,adsorbed state fluorine under competitive adsorption also provides an additional source of groundwater F-. However,the effects of evaporation and human activities on the elevated F-content of groundwater in the Yan’an Formation are small and negligible. The results provide a scientific basis for the safety of water quality for local drinking water and sustainable development of ecological environment. [ABSTRACT FROM AUTHOR]