Abstarct: In this work, we have studied the morphological, structural and optical properties of ZnS thin film grown on glass substrate by sol-gel (spin coating) and spray pyrolysis methods. In this study, we used the Field Emission Scanning Electron Microscopy (FESEM), X ray diffractometer (XRD) and UV-Vis spectrophotometer for charectrization of samples. In samples grown by sol-gel method, the effect of drying temperature on the structural and optical properties of ZnS thin films were studied.The XRD data for samples prepared by sol-gel (spin coating) indicated that all samples have amorphous structurss. Transmittance spectra showed the average transmittance of the samples is around %90. In samples grown by spray pyrolysis method, the effect of substrate temperature, flow rate of the solution and the effect of aluminum doping on structural and optical properties of ZnS thin films were investigated. XRD spectra recorded of all the samples prepared by spray pyrolysis method, indicated that all samples have cubic structure with preferred (111) orientation. FESEM images showed that substrate surface is completely covered with zinc sulfide with granular structurses. Investigation of deposition temperature effect indicated that the crystal structures for samples prepared at 500 is better than others and gap of the samples decrease from 3.8 ev to 3.5 eV with increasing substrate temperature. Study of the effect of the solution flow rate showed that this parameter has a significant impact on the structural and optical properties of the samples. By the increasing solution flow rate, average transmittance of the samples is significantly reduced and the direct band gap of samples decrease abut 200 meV. Study of the Al doped sample showed that transmittance increases with Al concentration up to 5 wt.% and decreases with further increase of aluminum doping level to 9 wt.%.