Abstract: Using laser alloying technology, Cr₃B₇Mo_x alloy composite coating was prepared on the 45 steel substrate.The results show that the coating structure is Fe-Cr, Fe₂B, Fe-Mo, and Cr_xFe_y phase.With the increase of Mo content, the microstructure at the bottom of the coating changes from coarse cell-like crystals to fine cell-like crystals, the microstructure of the core of the coating changes from coarse columnar crystals to dendritic polygonal dendrites, and the microstructure of the coating surface layer changes from cell-like crystals to polygonal fine equiaxed crystals.The hardness of the coating show a decreasing trend.The wear of the coating decreases first and then increases, and its wear resistance is the best, which is 0.72×10^-14 m³/(N·m).The wear mechanism of the coating is the combination of adhesive wear and abrasive wear.