Hard coatings deposited on metal substrates often occur crack and delamitation due to the higher residual stress accumulated on the interface of coating/substrate and also the inside of the coating. The effect of vacuum annealing on multilayered Ti/TiN coating deposited on TC4 titanium alloy substrate was studied in detail. Also the interface cracks under scratch load and sand erosion resistance were characterized. The results show that a multilayered Ti/TiN coating with weakened interface characteristic is obtained due the atoms diffusion on both side of the interface,which results in a decrease of hardness and increase of bonding strength. At the scratch load,the resistance of crack expansion along the interface is strengthened. And also the sand particles' "micro cutting"at small angle and fatigue effect at higher angle are restrained,so the sand erosion resistant of the annealed Ti/TiN coating is reinforced.