In this article, the N5/YSZ/NiCrAlY/( NiCrAlY+YSZ) /NiCrAlY/( NiCrAlY+YSZ) coatings were prepared on Ni-based single crystal alloy (Rene N5) by electron beam physical vapor deposition (EB-PVD). And the sampes were exposed to isothermal oxidation at 1000℃ for 200h and 500h. The microstructural evolution behavior and the mechanism of interface reaction was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The results suggest that the YSZ layer can form an α-Al2O3 active diffusion barrier layer with a “sandwich” structure to refuse the interdiffusion between substrate and mult-NY coating. And the mult-NY coating was transformed to mixed oxide layers gradually during the prcess of cyclic oxidation.