Thin Ce₂O_3film deposition was applied to 1Cr18Ni9Ti stainless steel. The effects of this treatment on the selective oxidation behaviour at 900℃ for 100h have been studied. The experimental results and metallographic analysis show that thin Ce₂O_3film significantly reduces the mass gain and spallation of the oxide scales and promotes the formation of a uniform and dense oxide scales, thus improves the high-temperature oxidation resistance of the stainless steel greatly. The effect of film deposited under 25V and 60s is a little better.