The effect of 5%Cr(mole fraction) on the scaling behavior of Ni-10Al was investigated at 900 ℃ and 1 000 ℃ with the aim to discuss the third element effect(TEE). The oxidation rate of the ternary alloy containing Cr is much slower than the corresponding binary alloys at both temperatures. A dense external scale of NiO overlying a zone of internal oxide precipitates forms on Ni-10Al, while Ni-5Cr-10Al develops a protective layer. So the addition of Cr promotes the formation of alumina scale. The possible mechanism of Cr on the oxidation of Ni-Al alloy is discussed.