Abstract: The hydrogeochemical characteristics of Fluorine in central Hebei Province are studied, The results show that there is a positive correlation of Fluorine concentration to temperature and Co₂ concentration in groundwater, so, except for the igneous province with high Fluorine content, temperature and Co₂ concentration are the major factors affecting Fluorine concentration. Inaddition, Ca²⁺ content in groundwater can also influence the F^- concentration due to the low solution of CaF₂, only the groundwater with nigh Na⁺/Ca²⁺ ratio favours the enrichment of F^-. Finally, it is pointed out that the preperation process of earthquakes might result in the variation of F^- concentration, and the possible precursors before several earthquakes in Qianniu-6 and other wells are discussed.