In this research work, a Molybdenum trioxide (MoO3) thin film of thickness 0.5μm was synthesized on a glass substrate by thermal vacuum evaporation technique. The deposition was performed at the rate of 1.2Ǻ/s. The structure and optical characterization of the film was carried out by XRD and UV visible spectroscopy respectively. The band gap of the film was 2.82eV. The results of XRD depicts sharp peaks at 2θ angles of 12.74◦ ,23.32◦,25.54◦,27.4◦,53.76◦ and 38.91◦ with respect to the planes (020),(110),(040),(021),(060) and (001).