AlSiN nano-composite coatings were prepared on TC4 Ti-alloy substrate by using multi-arc ion plating technique. The influence of N₂ flow rate and target-substrate distance on their microstructure, mechanical properties and corrosion resistance in 3.5%NaCl solution was investigated. The results show that the variation of plating process parameters influence the crystalline growth mode of the AlSiN coating. By longer target-substrate distances and higher N₂ gas flow the prepared AlSiN coatings exhibited higher crystallinity via a columnar grain growth mode, while a dense coating of finer grains or amorphous structure was obtained by shorter distances and lower N₂ gas flow rates. Comparatively, the AlSiN coating of higher crystallinity exhibits higher microhardness and excellent mechanical properties. The corrosion resistance of the coatings was influenced by the combined effects of crystallization growth mode and mechanical properties, namely the crystallization mode may affect the penetration of the corrosive medium and the formation of the surface oxide scale, while the mechanical properties may be related with the strength and the generation of defects of the coating. Electrochemical data indicate that the AlSiN nanocomposite coating prepared by a N₂ flow of 0.15 L/min and a target-substrate distance of 180 mm exhibited the optimal corrosion resistance, showing one order of magnitude reduction in corrosion current density compared to that of the TC4 substrate.