Abstract:Fluorine can inhibit growth of microorganisms. Fluorine stress test of eosinophilic Thiobacillus Ferrooxidans was carried out at different growth stage to investigate fluoride tolerance of microorganisms. The results show that when fluoride is introduced with F? concentration of 0.5 and 1.0 mmol/L respectively before lag period, Eh, Fe2+ oxidation rate and bacterial growth activity are similar to those of control group. When F? concentration is 1.5, 3.0 and 5.0 mmol/L, respectively, Eh and Fe2+ oxidation rate drop significantly until to being stagnant, and bacterial growth activity changes from bering slightly affected to absolute stagnation. When fluoride is introduced before logarithmic phase, bacterium show a significant delay when fluorine concentration is up to 10.0 mmol/L. Bacterium cannot grow normally when fluorine stress is 20.0 mmol/L.