The present invention relates to a catalyst for preparing phosgene and a method for preparing phosgene using the catalyst. Said method comprises: modifying the surface of an activated carbon coating/foamed silicon carbide structural catalyst using an alkali metal salt; filling the catalysts having different thickness of the activated carbon coating and different amount of the alkali metal salt in different sections in the axial direction of the multi-tubular reactor of the fixed bed, and preparing phosgene using Cl2 and CO. The radial and axial temperature difference of the catalyst bed is lowered by using the alkali metal salt-modified activated carbon coating/foamed silicon carbide structural catalyst and by segmental filling, so that high temperature of tube wall is obtained in the case of a larger tube diameter, and high quality of steam is obtained stably.