Zinc nitride (Zn3N2) thin films were prepared by radio frequency (RF) magnetron sputtering on quartz glass at different substrate temperatures. The structure and composition were characterized by X-ray diffraction and Raman-scattering measurements, respectively. The polycrystalline phase Zn3N2 films appeared when the ratio of the N2 partial pressure to the total pressure reached 1/2. The effects of the substrate temperature on the electrical and optical properties of the Zn3N2 films were investigated by Hall measurements and optical transmission spectra. The electrical and optical properties of the films were highly dependent on the substrate temperature. With the substrate temperature increasing from 100 to 300°C, the resistivity of the Zn3N2 films decreased from 0.49 to 0.023Ω · cm, the carrier concentration increased from 2.7 × 1016 to 8.2 × 1019 cm-3, and the electron mobility decreased from 115 to 32 cm2/(V · s). The deposited Zn3N2 films were considered to be n-type semiconductors with a direct optical band gap, which was around 1.23eV when the substrate temperature was 200°C.