Abstract: The (CdS)0.8Se0.2 thin films were prepared through using thermal evaporation technique onto rotating microscopic glass substrate. The obtaind samples are studied by X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and UV-VIS Spectroscopy. The micro structural futures are obtained with help of XRD pattern, which confirms the films are polycrystalline in nature having hexagonal structure. The AFM images revealed that, sample consists of well defined nano sized grains with almost uniform size distribution. SEM observation depicts the uniform distribution of grains and all the grains are spherical in nature. The absorbance spectrum exhibits absorption to be dominating mainly in visible spectrum. The variation of optical band gap was represented as a function of thickness.