Polvcrystalline antimony trioxide (Sb2O3) thin films with a thickness of 800nm, deposited on glass substrates at different temperature ranges 300-573 K, were optically characterized. The optical parameters such as refractive index. n, absorption coefficient, alpha, and optical band gap, E-g, were determined using the transmission spectra recorded in the range of 300-1400 nm and simple calculations based on Swanepoel's method including interference effect induced by multiple internal reflections in the substrate/thin film system. The effect of substrate temperature on the optical properties of Sb2O3 thin films has been studied. It was found that both refractive index and absorption coefficient depend markedly on the substrate temperature. The optical band gap energies and the corresponding allowed direct transitions have been determined from the absorption spectra. The correlations between optical parameters and the change in structure of the Sb2O3 thin films are discussed. (c) 2005 Elsevier B.V. All rights reserved.