The ZrO₂/Fe₃O₄ compounds have been developed as the adsorption materials for phosphate from the sewage water with high flow rate. Amorphous ZrO₂ and magnetite were main components of the ZrO₂/Fe₃O₄ compounds. The phosphated ZrO₂/Fe₃O₄ was prepared to evaluate the characteristics of surface charge after phosphate adsorption. The potentiometric titration of the ZrO₂/Fe₃O₄ and phosphated ZrO₂/Fe₃O₄ was performed in NaNO₃ electrolyte solution (0.01, 0.1, and 1 M) according to the backtitration method of Schulthess and Sparks (1986). The ZrO₂/Fe₃O₄-suspended solution was equilibrated for more than 6 hours after titration with HNO₃ and NaOH solution. The suspension pH of the ZrO₂/Fe₃O₄ was measured and H⁺ adsorption on the ZrO₂/Fe₃O₄ was plotted against pH. The surface charge and the point of zero salt effect (PZSE) of the ZrO₂/Fe₃O₄ and phosphated ZrO₂/Fe₃O₄ were given by the three titration curves and their intersections. The surface of ZrO₂/Fe₃O₄ and phosphated ZrO₂/Fe₃O₄ showed the negative charge below pH 6.4 and 5.7, respectively. The adsorption of phosphate provided the negative charge on the ZrO₂/Fe₃O₄. From the results of the percolation experiment using the 9.0 mg P L^-1 of phosphate solution (pH 7) with the 10 SV flow speed condition the ZrO₂/Fe₃O₄ compounds remarkably showed the typical breakthrough curve with 5.95 g P L^-1 of the breakthrough point. The desorption of phosphate from the phosphated ZrO₂/Fe₃O₄ was successively carried out by NaOH solution.