Abstract: Deposited Co-base self-fluxing alloy on 45 steel by laser cladding with YAG laser, microstructure and phase composition of cladding were studied by using optical microscope, scanning electron microscope and X-ray diffraction, and strengthening mechanism of Co-base self-fluxing alloy by laser cladding was present. The result of measuring micro-hardness of cladding is proved that property of laser cladding is meet to that of high-speed steel end mill.