Abstract Nanocrystalline cadmium sulfide (CdS) films were successfully prepared on glass substrates using chemical bath deposition (CBD) method. Many growth parameters have been considered in this work to specify the optimum conditions that affect optical properties of CdS films.Different thicknesses (100-230 nm) of deposited nanocrystalline thin films have been prepared using CBD technique. The thinner film has been annealed in vacuum for 1 hour at different annealing temperatures in the range of (250 - 400 °C) in order to study the role of annealing on some characteristics of CdS films.X-Ray Diffraction (XRD) has been used to characterize the structural properties of nanocrystalline CdS thin films. The diffraction peak was detected at 2th = 26.6° for nanocrystalline CdS .It was observed that the increase of the film thickness will increase the diffraction peak intensity which will in increase the grain size and intrudes good crystalline of the deposited films.The intensity of the diffraction peak is increased with the increased of annealing temperature which means that the crystalline as well as the grain size of the films is enhanced.