Abstract: Surface water or groundwater flowing through fluorine-rich rocks can easily lead to excessive fluorine in water.Excessive fluoride in water can cause endemic fluorosis, damage of the ecological environment and restrict comprehensive utilization of water resources.In this study, based on a highly effective fluoride removal agent developed by the research group earlier, the box-Behnken method of response surface analysis was applied to design fluoride removal experiments where the influences of pH value, dosage of defluoridation reagent and fast stirring time on fluoride removal effect were optimized.This paper used X-Photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FT-IR) to characterize the defluoridation reagent and the sludge produced after treatment, and discussed the mechanism of fluoride ion removal.The experimental results showed that F^-could be reduced from the initial 20 mg/L to 0.453 mg /L under the optimal conditions of fluoride removal (pH value 6.11, dosage 4.15 mL, fast stirring time 10.90 min), which was basically consistent with the predicted value 0.445 mg /L of the model.The defluoridation reagent was mainly through the formation of Fe, Al, Si and O polynuclear polyhydroxyl complex, fluorine-ion exchange with hydroxyl and replace hydroxyl, then fluorine-ion was fixed in the polynuclear polyhydroxyl complex.Meanwhile, fluoride forms a tetrahedral structure of aluminum, silicon and oxygen, and locks fluorine ions in the tetrahedral structure to achieve fluoride removal.Compared with the current main treatment process using hydroxyapatite adsorption, the defluoridation reagent in this study has the advantages of simple treatment process, stable treatment effect and low treatment cost.