The invention provides a catalyst for catalytic removal of carbon monoxide and formaldehyde under conditions of ambient temperature and humidity, and belongs to the technical field of catalyst for harmful gas. The catalyst is a supported noble metal catalyst formed by depositing an active component of noble metal on a spinel-structure oxide support containing an aid, wherein the spinel-structure oxide support is one or two of magnesium ferrite, calcium ferrite, strontium ferrite, barium ferrite, cobalt ferrite, nickel ferrite, copper ferrite, zinc ferrite and manganous ferrite; the active component of noble metal is elemental platinum or platinum oxide, and the aid is an oxide of sodium. The catalyst can catalyze carbon monoxide and formaldehyde for complete oxidation under the conditions of ambient temperature and humidity, and products only comprise carbon dioxide and water. The catalyst has higher stability, the activity cannot be reduced after the catalyst is stored for a long time, and the catalyst is not required to be reduced before use; the catalyst has the advantages of being easy to prepare, good in product repeatability, convenient to store and transport and the like and has quite good application prospect.