α-Bi2O3 thin films were deposited on different substrates by atomic layer deposition method. The results of X-ray diffraction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscope correspond to α-Bi2O3. The Fourier transform infrared spectroscopy analyses indicate that the reaction is rather complete during the deposition. Optical properties of the films have been investigated using ultraviolet-infrared transmittance spectra in the temperature range of 8–300 K. It is found that the band gap Eg decreases from 3.12 to 3.03 eV with the temperature. The parameters αB and ΘB of the Bose-Einstein model are 69.3 meV and 293.9 K, respectively. The band narrowing coefficient dEg/dT is −0.435 meV/K at room temperature. The present results can be considerable for future application of Bi2O3-based electro-optic and wide temperature range optoelectronic devices.