Natural zeolite was modified with sulfuric acid, sodium hydroxide, and ferric chloride solution, respectively. Defluorination ability of modified zeolite was studied through adsorption experiments. The optimal condition for modification of the natural zeolite was determined. The specific surface area and pore size distribution of the zeolite before and after modification were compared. The composition and content of elements in the natural zeolite and ferric chloride modified zeolite were determined using XRF. The results showed that ferric chloride was the best for fluoride removal from the natural zeolite. The fluoride adsorption rate of ferric chloride from the zeolite can be expressed with pseudo-second-order kinetics. The equilibrium adsorption data fitted well to Langmuir adsorption isotherm with the maximum fluoride adsorption capacity of 0.087 mg·g^-1, which was greatly improved compared to the unmodified zeolite. The equilibrium constant was 0.28 L·mg^-1. The specific surface area of the modified zeolite decreased and the content of Fe element increased, while Ca^{2 +}, Mg^{2 +} content reduced, indicating that the mechanism of fluorine removal is mainly resulted from chemical adsorption and complicated ion exchange.