We have studied the catalytic combustion of carbon particulates over Mg ferrite catalysts prepared by the malic acid method. The catalyst was modified to enhance the catalytic activity by the substitution of alkali metal ions into Mg sites. In the MgFe2O4 catalyst, the partial substitution of alkali metal ions into Mg sites enhanced the catalytic activity for the combustion of carbon particulates. It decreased in the following order Cs > K > Na. In Mg1-xCsx Fe2O4 catalysts, the catalytic activity increased with the increase of x and was almost similar at x > 0.2. The partial substitution of Mn into Fe site enhanced the oxidation rate of carbon particulates.