Currently, Ni-based superalloys are widely applied to turbine blades or other components of gas turbines for their excellent high temperature mechanical properties. These components must exhibit a high level of resistance to the oxidation and corrosion conditions generated by the combustion environment. The general design philosophy is to select a high strength substrate alloy to withstand the stress and apply a surface coating to give maximum protection from the environment. In this work, a Cr-modified aluminide (Al-Cr) coating were prepared by combining arc ion plating and pack cementation aluminizing. As a contrast, a simple aluminide coating was developed by pack cementation aluminizing. The isothermal oxidation behaviors at 1000 and 1100 ℃ were investigated on the Ni-based superalloy DSM11 substrate, aluminide coating and Al-Cr coating. The results demonstrate that aluminide coating and Al-Cr coating are dense and adhere tightly to the substrate. The microstructures of aluminized coating and Al-Cr coating are divided in two distinguished areas: the outer layer and the interdiffusion zone. The outer layer of the aluminized coating is composed of b-NiAl and Ni₂Al₃ phases, while the Al-Cr coating consists of b-NiAl, Ni₂Al₃, a-Cr and AlCr₂ phases. The DSM11 substrate shows bad oxidation behavior at 1000 ℃ isothermal oxidation test. The aluminide coating and Al-Cr coating both possess good oxidation properties in this test. Compared with aluminide coating, Al-Cr coating exhibits much better oxidation behavior due to the formation of Cr(W) zones, which can delay the process of Al depletion by hindering the diffusion of Al from the coating to the substrate. As for 1100 ℃ isothermal oxidation test, a large amount of mixed oxides include NiCr₂O₄ spinel and a-Al₂O₃ form on the surface of DSM11 substrate. The oxide scale on the surface of aluminide coating is simplex a-Al₂O₃ at the initial stage, while prolonging the oxidation time it changes into less protective mixed structure composed of NiCr₂O₄ spinel and a-Al₂O₃ with massive internal oxidation, leading to great degradation and even failure of the coating. The surface of Al-Cr coating is covered with thick a-Al₂O₃ during the whole oxidation process. The localized scaling zones produced during oxidation are re-covered by newly formed a-Al₂O₃. It benefits from the third element effect of Cr, which implies that the Al-Cr coating degenerates primarily by consuming Al-reservoirs. Moreover, the presence of Cr can promote the selective oxidation of Al and the self-repair abilities of the coating.