Ni20 alloy cladding was prepared on the 45 steel by laser cladding technology. The phase structure, structrue and high temperature oxidation resistance of cladding were studied. The result shows that the etallurgical bonding between the coatings and the substrates is excellent; The cladding structure has rapid directional solidification, the growth direction of grain is perpendicular to the interface, the coating are mainly built up by CrNiFeC,Fe3Ni2,Ni3Cr2.Dense oxide film are formed when Ni20 alloy cladding layer inhigh-temperature oxidation, which improves high temperature oxidation resistance.