Highly crystalline and transparent Cadmium Sulphide (CdS) thin films were deposited on microscopic glass substrates by sol- gel spin coating technique. Effects of annealing time on structural and optical properties of the films were studied. Data obtained from XRD patterns are used to identify the phase, crystal structure, grain size and lattice constants of the films. There is a preferential orientation of the crystallites in the film along c-axis (perpendicular to the plane of the substrate) producing a strong hexagonal (0 0 2) peak. The crystallite size obtained through the XRD analysis was found to increase with increase in annealing time, varying from 6.1 nm to 9.3 nm. The size of the particles estimated also from the band gap values obtained from optical study, using the Brus equation was found to be in the range of 5.0 nm to 9.6 nm. The photoluminescence spectra show presence of defect structures and the CdS emission spectral peaks are found to decrease in intensity, with increase in annealing time. These results suggest that the deposition of CdS thin films should be further investigated for application towards the fabrication of optoelectronic devices