Abstract: In order to prepare nickel-based WC composite coating with excellent forming quality and mechanical properties on 42 CrMo, Taguchi design test method was used to explore the influence of process parameters on the properties of nickel-based WC composite coating. The laser power, powder feeding rate, and scanning speed were set as influencing factors, and dilution rate and microhardness were set as response indexes. The results show that the laser power has the greatest effect on the dilution rate and microhardness of the composite coating, followed by powder feeding rate and scanning speed. When the laser power is 2000 W, the scanning speed is 10 mm·s^-1, and the powder delivery rate is 1.4 r·min^-1, the microstructure of the coating is uniform and dense, and the segregation of W, C and Nb elements appears between the crystals,and a large amount of W element is precipitated near the WC particles. The formation of WC, W₂ C, NbC and other hard phase carbides makes the microhardness of the composite coating about 1.7 times than that of the matrix. The wear mechanism of the composite coating changes from adhesive wear to abrasive wear, and the friction coefficient decreases about 0.12 compared with that of the matrix, which significantly improves the mechanical properties of 42 CrMo.