Study on laser alloying of Si₃N₄/graphite composite coating on 45carbon steel has been carried out in this paper. The microstructure, micro-hardness, contents and distributions of elements and tribological performance of coatings have been analyzed and studied. Based on these analyses, the ingredients and proportion of powders in pre-coatings and parameters of laser alloying are optimized. The results show that laser alloying of Si₃N₄/ graphite can attain high quality coating with uniform microstructure and increased hardness. And the alloyed coatings have lower friction coefficient, higher wear resistance, stronger anti-cohesion and steady tribological process under dry friction condition.