NOVELTY - Unsaturated hydrocarbon hydrogenation catalyst comprises a carrier, and a main metal active component and an auxiliary metal active component loaded on the carrier. The main metal active component and auxiliary metal active component are obtained by reducing the main metal active component precursor and auxiliary metal active component precursor loaded on the carrier by using ionizing radiation. The main metal active component is in monomer state. The main metal active component is palladium, which is 0.01-1 wt.% of the total weight of the carrier.    USE - The catalyst is useful in 3-8C straight chain unsaturated hydrocarbon hydrogenation, preferably in 4-5C unsaturated hydrocarbon hydrogenation to generate alkane (claimed).    ADVANTAGE - The catalyst has high activity and selectivity, and does not require pre-reducing with hydrogen and can be directly used.    DETAILED DESCRIPTION - Unsaturated hydrocarbon hydrogenation catalyst comprises a carrier, and a main metal active component and an auxiliary metal active component loaded on the carrier. The main metal active component and auxiliary metal active component are obtained by reducing the main metal active component precursor and auxiliary metal active component precursor loaded on the carrier by using ionizing radiation. The main metal active component is in monomer state. The main metal active component is palladium, which is 0.01-1 wt.% of the total weight of the carrier. The auxiliary metal active component comprises: (i) at least one of lead, copper, zinc, silver, manganese, molybdenum, gold and bismuth, which is 0.01-5 wt.% of the total weight of the carrier; and (ii) at least one of lithium, sodium, potassium, magnesium, calcium and barium, which is 0.01-3 wt.% of the total weight of the carrier. The average diameters of the main metal active component palladium particles and the auxiliary metal active component particles are less than 15 nm. An INDEPENDENT CLAIM is also included for the preparation of the unsaturated hydrocarbon hydrogenation catalyst, comprising exerting ionizing radiation to a system comprising main metal active component palladium precursor, the auxiliary metal active component precursor, the carrier, the free radical scavenging agent and water, to at least reduce the main metal active component palladium precursor to elemental palladium.