The characteristics of Sub/NiCrN_x/Ag/NiCrN_x/SiN_x/Air multilayer structure of silver reflector prepared by magnetron sputtering are studied and the influences of N₂ on the spectrums of Ag thin film, dielectric protective layer and silver mirror are analyzed. The reasons to cause low reflectance of the silver films at short-wavelength region (400~500 nm) are investigated via depth profiling with X-ray photoelectron spectroscopy and transmission electron microscope. The influences of N₂ proportion of Ar/N₂ on the optical properties, surface topography and crystal structure of prepared single-layer silver films are investigated during sputtering deposition via spectrophotometry, scanning electron microscopy, and X-ray diffraction. Moreover, the reflectances of prepared-silver mirrors prepared by different gas flow ratios of Ar/N₂ plasma are compared and the stoichiometric ratio of SiN_x thin films is analyzed. Experimental results proves that, the stoichiometric ratio of SiN_x thin films is ameliorated when the silver target is sputtered with the plasma of mixed argon and nitrogen. The reflectance of the prepared silver mirrors at 400 nm wavelength is improved from 71.7% to 79.3% as the N₂/Ar gas flow ratio changed from 0 to 40%. Furthermore, the silver mirrors prepared by magnetron sputtering in Ar/N₂ plasma present excellent corrosion resistance and environmental stability.