TiN, Ti 1−x Al x N single layer coatings and TiN/Ti 1−x Al x N multilayer coatings were deposited on SKH51 tool steel substrate by arc ion plating. The coatings were annealed in air to study the effect of aluminum and film structure on the oxidation performance. The surface morphology and structure were characterized by scanning electron microscopy and X-ray diffraction. The element distribution on the cross section was analyzed by electron probe microscopy. It is found that the oxidation resistance of these Ti 1−x Al x N based coatings is mainly attributed to aluminum content in them. In comparison with the Ti 1−x Al x N single layer coating, the TiN layer inserting into the Ti 1−x Al x N in a multilayer coating increases the tendency of Ti diffusion toward the surface and forms a Ti-enriched top surface oxide layer, thus degrades the oxidation resistance. As far as the oxidation resistance is concerned in this study, Ti 0.33 Al 0.67 N single layer coating performs the best among all coatings. The kinetic of oxidation behavior of all coatings presents two definite stages. One is a slow oxidation growth which conforms to parabolic law, and the other presents severe mass gain with oxidation duration. The annealing time for severe oxidation initiation is responsible to Fe 2 O 3 formation in the oxide scale.