Abstract: To solve the problem of achieving the large diameter amorphous metallic film first mirrors, based on the research of Co61.2B26.2Si7.8Ta4.8 metallic glass, splicing the amorphous glass bulks together as the target and using bulk amorphous glass as the sputtering material, by unbalanced magnetron sputtering coating method, the Co61.2B26.2Si7.8Ta4.8 amorphous metallic film first mirrors was realized. The research results show that with designing the composition and synthesis target-material, amorphous film first mirrors having the same optical properties with BMGs can be achieved; with coating Cr on the amorphous film, the spectral reflectivity of amorphous metallic film first mirrors in visible spectrum can be further increased.