Abstract: The adsorb defluoridation experiment, performed by using pig ash of phosphorite with hydroxy, fly ash from honeycomb briquette and hematite, demonstrated that pig ash of phosphorite with hydroxy easily produced excellent effect, fly ash from honeycomb briquette took second place and hematite performed worse. The maximum fluorine adsorption of pig ash of phosphorite with hydroxy could reach 1.28mg/g and 1.00mg/g made by fly ash from honeycomb briquette. The minimum of effluent fluorine of pig ash of phosphorite with hydroxy is 0.39mg/L, with 94.3% defluoridation. By fly ash from honeycomb briquette, fluorine can be 4.25mg/L at the lowest, close to the Beijing Tertiary Emission Standard. In different pH values, the results indicated that, in acidic condition, adsorption of fly ash from honeycomb briquette could be much improved, and effluent fluorine reducing remarkably was 1.44mg/L. The effect of pH changing on defluoridation by pig ash of phosphorite with hydroxy was less. Isothermal adsorption curve of fly ash from honeycomb briquette and pig ash of phosphorite with hydroxy represented Second Kind Curve summarized by Tang Shouyin, which showed adsorption is made by multi-layer molecule. Based on fluorine adsorption and effluent fluorine of fly ash from honeycomb briquette and pig ash of phosphorite with hydroxy, the authors estimated coefficient of B.E.T. expression in isothermal adsorption curve.