NiCrBSi coating was prepared on the surface of 45 steel by CO2 laser. The microstructure of the clad layer was characterized by SEM、EDS and XRD. The microhardness and wear resistance of the laser clad layer was examined. The results show that laser clad layer can be achieved under technical processing parameters and that the good metallurgical bonding is formed between the coating and substrate. The coating is uniform, continuous and free of pores and cracks. The microstructure of the coating is mainly composed of g-Ni, Ni3B, CrB and Cr23C6 particles. The microhardness of the coating (500～650HV0.2) is distinctly higher than that of the substrate(240～250 HV0.2). The clad layer is reinforced by particles and grain-refining, resulting in greatly increase in wear resistance comparing with 45 steel.