In this work the microstructures and high temperature oxidation behaviors of Co-Cr-Y modified pack aluminide coatings on Ni-based superalloy GH586 were investigated. The results indicated that the specific Co-Cr-Y-modified aluminide coating had a mass gain of only 0.36 mg/cm₂ after oxidation at 1000 °C for 100 h, it was much less than that of the substrate at 1000 °C. From the X ray diffraction the phases of the coatings were mainly AlNi, and after oxidation for 100h at 1000 °C the denser oxidation scale was composed of Al₂O₃, Cr₂O₃, and CoCr₂O₄. The surface and cross sectional morphologies were characterized by scanning electron microscope (SEM). The coating exhibited the better high temperature oxidation resistance, compared to the oxidation film of GH586 without coating. Moreover, the growing Cr (w) rich phase was gradually gathered in the grain boundaries during the oxidation, it is beneficial to provide more Cr element for the dense oxidation film, which is mainly attributed to the excellent high temperature oxidation resistance.