Abstract: The effects of thicknesses of AlON layer on microstructures and properties of TiAlN/AlON nanomultilayers were studied. TiAlN/AlON nanomultilayers had been deposited on HSS (W6Mo5Gr4V2) by magnetron sputtering system. The microstructure and properties of these nanomultilayers were characterized by X-ray diffraction, vickers hardness tester and universal surface tester. The results show that under "template effect" of TiAlN, amorphous AlON has been crystallized and grow epitaxially with TiAlN. The superhardness effect could be generated in the region with sharp interface. When the thickness of AlON layer is 0.81 nm, the nanomultilayer has highest hardness. The hardness of nanomultilayer is 3 769.6 HV and increases 60.37% than TiAlN coating. When the thickness of AlON layer is bigger than 0.81 nm, the hardness decreases with thickness of AlON layer. The scratch resistance and abrasion resistance are best when the thickness of AlON layer is 0.81 nm.