Abstract: In order to study hydrogeochemistry of the fluoride in groundwater in northern Lianyungang area, the authors analyzed 63 groundwater samples and investigated the distribution and genesis of high-fluoride groundwater. The results show that the concentration of fluoride in groundwater tends to increase with the groundwater flow. The high-fluoride groundwater areas are distributed in low gulf plain and depression. The alkaline water environment with high concentrations of sodium and bicarbonate is the main factor responsible for fluoride enrichment and transfer of fluoride from sediments to groundwater. The formation of high-fluoride groundwater results from prolonged geological and geochemical evolution. The hydrogeochemical processes including mineral dissolution and precipitation, evaporation and concentration, cation exchange and adsorption are the dominant factors for the enrichment of fluoride in groundwater.