CdS films of different thicknesses (d ≈ 100–300 nm) are deposited on the glass substrate by thermal evaporation technique. The structure of these films had been studied by Rietveld refinement and atomic pressure microscope. The films of CdS/glass show a wurtzite type structure. XRD calculations show that the lattice parameters a and c have changed, the microstrain decreases, and the crystallite size increases. The optical constants refractive index n, and extinction coefficient, k consequently band gap are estimated from SE via construction an optical model. The refractive index n of the CdS/glass films received from SE model increases with growing of CdS layer thickness that is credited to the rise of the size of the crystal. It was also found that when the thickness of the CdS layer increases, the general behavior of the extinction coefficient k of the CdS/glass film increases. In addition, it is found that the direct