Abstract: Vacuum induction melted Inconel718 alloy was refined by electron beam smelting. The high temperature oxidation behaviour of the alloy before and after electron beam refining was studied and compared by isothermal oxidation tests in the air at 900, 1 000℃. The results show that the average oxidation rate of the electron beam refined alloy oxidized at 900℃ for 120 h was 0.366 20 g·m^-2·h^-1, smaller than that before refining; the oxidative activation energy was 280.90 kJ·mol^-1, higher than that before refining. The outer layer of the oxide film of the electron beam refined alloy oxidized at 900℃ and 1 000℃ for 120 h was composed of Cr₂O₃ and TiO₂, the middle layer consisted of Cr₂O₃ and a small amount of TiO₂ and spinel NiCr₂O₄, and the inner layer was mainly composed of Al₂O₃. The content of trace impurity elements distributed evenly in the electron beam refined alloy was relatively small, grain size was larger,and the alloy had a better antioxidant property.