Abstract: Ni-8Al-xMo (x=0,5,10,15,mass fraction/%) superalloys were prepared by powder metallurgy technique, and then isothermally oxidized at 1 000℃ for 100 h. The surface and cross-section morphology of oxide films was observed and the phase composition was analyzed. The high temperature oxidation resistance of the tested alloys was studied. The results show that the high temperature oxidation resistance of the tested alloy with molybdenum addition was better than that without molybdenum addition. The oxidation products on the surface of the tested alloy were mainly Al₂O₃ and NiO, with a small amount of NiAl₂O₄ and NiMoO₄. When the mass fraction of molybdenum reached 10%, the oxide film on the surface of the tested alloy showed spalling features at different degrees. When the mass fraction of molybdenum was 5%, the high temperature oxidation resistance of the tested alloy was the best.