Silicon Nitride thin films were deposited on glass substrates by r.f. magnetron sputtering with a mixture gas of N2 and Ar. The properties of the thin films vs substrate temperature have been investigated. The phase structure, surface morphology, chemical composition, thickness and optical properties of the films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS), ultraviolet-visible spectroscopy (UV-Vis) and nkd-system spectrophotometer. The results show that the films appear amorphous and crystalline structure at the substrate temperature of 20 and 300 , respectively, the atomic ratio of Si to N of the films is nearly 1:1, the transmittance in the ultraviolet-visible region is above 75%; with increasing substrate temperature the refractive index and the optical band gap increase, and the deposition rates of the films decreases.