The invention discloses an unsaturated hydrocarbon hydrogenation catalyst and a preparation and use thereof. The unsaturated hydrocarbon hydrogenation catalyst is prepared by ionizing radiation reduction of a metal active component precursor supported by a carrier, wherein a main metal active component is a monomer; and the average diameter of the metal particles is less than 15 nanometers. The catalyst disclosed by the invention has the advantages of high activity, no need of reduction by hydrogen in advance, direct use, and the like.