In 2 O 3 :Sn (ITO) films were deposited on quartz substrates by direct current magnetron sputtering and annealed in N 2 at temperatures ranging from 150 to 350 โข C for 1 h. The structure and morphology of the films were investigated by X-ray diffraction and atomic force microscopy. The results demonstrate that the as-deposited films are polycrystalline structure and the crystallinity can be apparently improved after annealed above 250 โข C. The electrical and optical properties of the films were also studied by van der Pauw method and spectrophotometer, respectively. It is found that the carrier concentration increases and mobility decreases, respectively, after the films have been annealed at high temperature. As a consequence, the resistivity changes from 14.80 ร 10 -4 cm for the as-deposited film to 3.99 ร 10 -4 cm for the film annealed at 350 โข C. Furthermore, even the optical absorption in the near-infrared region increases for the annealed films, the high quality of transmittance (more than 90%) within the visible region can be retained. The measured transmittance data were also simulated very well based on the modified Drude and Forouhi-Bloomer models. Additionally, the electrical parameters calculated from the optical simulation, such as carrier concentration, mobility, and resistivity, are in good agreement with those obtained electrically by van der Pauw method.