Abstract: The kinetics of the reduction of phosphate in molten slag by solid carbon,carbon in liquid iron saturated with carbon and phosphorus and CO gas was studied. Under the conditions of slag basicity CaO/SiO2 = l. 1,and A12O3 around 8. 3% ,the reaction rate constant of reduction of phosphate in molten slag by solid carbon was expressed byThe rate constant increased with the slag basicity. The rate constant of phosphate reduction by carbon in liquid iron saturated with carbon and phosphorus was about ten times larger than that by solid carbon under the same conditions. The reduction rate by CO gas only depended on the flow rate of CO gas. Its reduction reaction was close to thermodynamic equilibrium.