Abstract: The Ti-Al-N coatings were synthesized by arc magnetron co-sputtering on Ti600 alloy substrate.The influence of the annealing and Ti/Al ratio(controlled by sample revolution speed)on the microstructures,thickness and phase-structures was investigated with X-ray diffraction,energy dispersive spectroscopy and scanning electron microscopy.The results show that the synthesis conditions had a major impact.To be specific,as the Ti/Al ratio decreased,the as-deposited Ti-Al-N coatings became increasingly smooth and compact because of the decreases of droplet and pit densities and because of reduction of grain-size;the Ti₂AlN phase and thickness changed in an increase-decrease manner after annealing.Moreover,the depth profiles of Al and O varied in an increase-decrease mode,at a depth≥6 μm,Ti-and N-contents significantly increased.We suggest that the optimized Ti/Al ratio be 2.36 in growth of Ti₂AlN-phase dominant coatings.