Copper nitride (Cu3N) thin films were deposited on glass substrates by reactive radio frequency magnetron sputtering under different radio frequency power (P) and nitrogen partial pressure r(r=N2/［N2+Ar］). The thickness, crystalline structure and surface morphology of films were characterized by profilometer, X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The optical transmission spectrum was obtained by an ultraviolet-visible (UV-VIS) spectrophotometer and the optical band gap (Eg) was calculated. The results suggest that the films' deposition rate increases with P and r. The surface of the films reveals a compact structure, and the grain size of Cu3N is about 30nm. Meanwhile, with increasing r, the grain size and optical band gap of Cu3N increase, of which Eg ranges from 1.47 to 1.82eV, and the films' growth prefers the (111) direction at low r and the (100) direction at high r.