To improve the high temperature oxidation resistance of STD61 steel used as hot dies or cutting tools, CrN films of single phase with the (111) preferred orientation which were deposited on STD61 steel substrates by arc ion plating. The oxidation characteristics of CrN films were studied at the temperatures, ranging from 800 to 950 ℃ in air(70sccm) by employing thermogravimetry. XRD, SEM and EPMA The high temperature oxidation resistance of STD61 steel was improved by the CrN films. The oxidation of CrN films follows nearly parabolic rate laws and the activation energy of oxidation was 206 kJ/㏖ at the temperatures ranging from 800 to 950℃. According to the marker test using Al₂O₃, particles, the conclusion of investigation for the interface migration of oxide was that the growth of oxide(Cr₂O₃) is controlled by external diffusion of cation(Cr ion)