Co-Zr multilayered thin films were prepared by three-gun magnetron sputtering system and low temperature arrorphization was attempted. According to thin film X-ray and cross-sectional TEM analysis, it has been found that zirconium layer is arrorphized by diffusion of cobalt and the amorphization rate at the upper interface is two or three times faster than that at the lower interface of the zirconium layers. This new phenomenon is explained in terms of atomic mixing during sputtering.