Abstract: In order to improve the wear resistance of TC21 titanium alloy, Ti-Al-Co/(Si₃N₄)_x(x=4wt%, 6wt%, 8wt%,10wt%) composite coatings were prepared on the surface of TC21 titanium alloy by laser cladding technology. The effects of Si₃N₄ addition content on the microstructure, microhardness and wear resistance of the composite coating were investigated. The microstructure and phase composition of the cladding layer were analyzed by X-ray diffractometer(XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The microhardness and wear resistance of the cladding layers were tested by Vickers hardness tester and a comprehensive material performance tester. The results show that the cladding layer has good metallurgical bonding with the TC21 substrate. The microstructure of the cladding layer mainly consists of planar crystal and equiaxed crystal, and its phase composition is primarily composed of Ti₃Al, β-Ti, TiAl, CoTi, TiN, Ti₅Si3 and Ti₂AlN. With the increase of Si₃N₄ content, the morphology of TiN changes from granular to dendritic, and the in-situ generated Ti₅Si₃ is dispersed in the cladding layer. When the content of Si₃N₄ is 10wt%, the microhardness of the cladding layer is largest, and the hardness is 1.39 times higher than that of the substrate. When the content of Si₃N₄ is 8wt%, the wear resistance of the cladding layer is best, and the wear resistance is 2.16 times higher than that of the matrix.