During conventional iron making, the temperature exclusively determines the oxygen potential in a blast furnace hearth because of carbon saturation. Consequently, impurities such as phosphorus are reduced and remain in the iron because of the excessively low oxygen partial pressure, which can be controlled using gaseous reductants such as hydrogen and carbon monoxide to produce solid iron because of the low carbon content. We previously investigated the equilibrium distribution of phosphorus between the solid iron and molten slag at 1 623 K by varying the oxygen partial pressure and the basicity of the slag, and the phosphorus content in the solid iron was sufficiently low under the experimental conditions. In this study, the phosphorus distribution behavior was investigated when solid iron was obtained by reducing Al2O3-CaO-FetO-MgO-SiO2 molten oxide, and the system was evaluated based on Fe loss.