Theoretical analysis of the optical and Solid State properties of Antimony Selenide (Sb2 Se3 ) thin film using beam propagation technique in which a scalar wave is propagated through the material thin film deposited on a substrate with the assumption that the dielectric medium is section into a homogenous reference dielectric constant term, εref and a perturbed dielectric term, ∆εp (r) representing the deposited thin film medium is presented in this work. These two terms, constitute arbitrary complex dielectric function that describes dielectric perturbation imposed by the medium for the system. This is substituted into a defined scalar wave equation in which the appropriate Green’s Function was defined on it and solved using series technique. The field value obtained from Green’s Function was used in computation the propagated fields for different wavelength within three windows of electromagnetic wave spectrum during which the influence of the dielectric constants of Sb2 Se3 thin film on the propagating field was considered. The results obtained from the computation were used in turn to obtain the data that were used in turn to compute the band gaps, solid state and optical properties of the thin film such as reflectance, Transmittance, reflectance and band gap of the thin film.