Abstract: On the basis of the mechanism proposed in paper ( I ), a mathematical model of intrinsic kinetics for SO2 oxidation on "K-V" and "K-Na-V" catalysts has been obtained: The intrinsic kinetics of the reaction was studied using the internal recirculation reactor TG-1 developed by the authors over broad reactant concentrations and temperature ranges. By graphical, linear- and weighted-least square methods, ten types of competitive models with more accurate initial values of parameters were obtained from seventeen types of kinetic equations, including the authors model. Then, computing with Powells optimum program under the same conditions, we found that the authors model is optimal for both low and high temperature ranges for SO2 oxidation with the two catalyst series. The optimum rate equation was validated through analysis of ( 1 ) the results of the single variable experiments, ( 2 ) the physical meaning of the parameter values in the optimum model, and (3) the rate-data residual errors over a wide range of gas compositions and temperatures.