Isothermal oxidation behavior of CoNiCrAlYRe alloys with different aluminum content at 1000 oC in air was investigated by X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy analysis. The results show that increasing of the aluminum content induces the Cr-rich phase to precipitate at the γ/β interfaces. The formation of the spinel oxide scales is significantly suppressed by the increase of the aluminum content. The existence of the Cr-rich layer is beneficial for the formation of a compact oxide layer of the alloy with high aluminum content, which lowers the oxidation rate and improves oxidation resistance