Abstract: Abstract：Since Mesozoic-Cenozoic, great thickness of Tertiary and Quaternary sediments has been deposited in Songnen fault basin, which has constituted the foundation of water storage structure for the phreatic and confined water. There exists high fluoride in the phreatic and Quaternary confined water, with the fluoride in 194 samples ranging from 0.25 to 14 mg/L (3.45mg/L on average). Large-scale prevalence of fluorosis has resulted from the drinking of high fluoride water. The researches conducted by the authors show that high fluoride groundwater is mainly distributed in the piedmont area, the evaporation discharge zone and the transitional zone in the middle of Songnen basin, where evaporation is strong. In this area, the groundwater hydrochemistry is of HCO3-Na · Mg and HCO3-Cl · Na types, and the total dissolved solid is about 689.84-2005.6 mg/L. The formation of high fluoride water is related to climate, hydrology, geological structure, rock and soil, geological and hydrological conditions of water chemistry and other natural factors, and is also affected by human activity factors such as the irrational exploitation of groundwater. The research on the groundwater environmental characteristics and causes of high fluoride is very important for the effective implementation of safe water supply.