Preparation of carrier: α-gibbsite and aluminum monohydrate water are used as raw materials, fluxing agent, mineralizer and carbon-containing materials are added, and water and methyl cellulose are mixed for kneading, and then formed, dried and calcined to obtain carrier corundum, and the carrier is impregnated with silver compounds and other components, and then calcined and decomposed and screened to obtain the finished product.