Abstract: In this experimental research,it is introduced that a 5kW CO2 laser with transverse flow for cladding Ni base alloy coat on austenite basic of the sealing surface of medium and high pressure valve for petrochemical industry.After processed by the laser cladding,the laser cladding coat of 3mm thick can be mede with a smooth surface.The test and comparison analysis indicated that the microstructure and all the performance have obvious advantages over the spurt welding processing.