Optical properties of chromiumoxide Cr2O3 thin filmswhich were prepared by the spray pyrolysis method have been experimentally characterized, the films were deposited onto a glass substrate at a temperature of 450 °C by spray pyrolysis technique. The as-prepared film was annealed at a temperature 550 °C. Transmittance spectra were used to determine the optical constants of the films, and the effects of the annealing temperature on the optical constants were investigated. Transmittance measurements show that the absorption edge suffers a red shift and the optical constants of Cr2O3 films increases as the annealing temperature increased to 550 °C. The singleÂoscillator parameters were also determined. The change in dispersion was investigated before and after annealing. The optical energy gap decreased from 3.08 to 2.95 eV after annealing.Analysis revealed that the transition is indirect allowed one.