Near-infrared-ultraviolet optical properties of Sn0.925Mn0.075O2 (SMO) film grown on c -plane sapphire substrate have been investigated by the transmittance spectra in the photon energy of 0.45-6.5 eV (190-2650 nm) from 5.3-300 K. The optical constants have been extracted by fitting the experimental data with the Adachi's model. The optical band gap of the film can be estimated from the relation (αE )2proportional to(h υ-E g). It is found that the absorption edge shifts to a lower energy side with increasing the temperature and the band gap E g decreases from 3.80 to 3.72 eV. The parameters αB and θB of the Bose-Einstein model are 45.4 meV and 221.8 K, respectively, which could be ascribed to the thermal expansion of crystal lattice and the carrier-phonon interaction. The band narrowing coefficient dE g/dT of the SMO film is estimated to be -3.92x10-4 eV/K at room temperature.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.