Copper nitride films were prepared on glass by reactive direct current magnetron sputtering at various Ar/N 2 contents at room temperature. Optical reflectance and transmittance spectra have been obtained in the range 200-2000 nm. The optical properties of the deposited films are influenced by the N 2 partial pressure significantly. The optical transmittance of the films increases with increasing the nitrogen contents. Also by increasing the amount of nitrogen in working gas, the optical absorption coefficient of Cu 3 N films was increased. The optical band gap of the films is estimated by the absorption coefficients values at the absorption edge using Tauc's procedure. For deposited films both real (n) and imaginary (k) parts of the complex refractive index are calculated.