Abstarct: In this thesis, we have studied the structural and optical properties of ZnSe thin film grown by spray pyrolysis method on glass substrate. The effects of various parameters such as: the solution flow rate (4, 8 and 10 ml/min), Volume of the solution (50, 75 and 100 ml), Substrate temperature (380, 400 and 420 ͦC) and annealing and also the presence of Aluminum impurities on the structural and optical properties were studied. We have used the Field Emission Scanning Electron Microscopy (FESEM), X-ray diffractometer (XRD) and UV-Vis spectrophotometer for charectrization of samples. The XRD results, showed that samples have polycrystalline cubic structure with (111) preferential orientation. Investigation of the solution flow rate effect indicated that this parameter has a significant impact on the structural and optical properties of the samples: by increasing the solution flow rate, the polycrystalline structure changes into an amorphous structure and the direct band gap of samples increase abut 130 meV. Reduction of the solution volume also causes decrease in the crystallinity of the samples and increase in band gap. Investigation of deposition temperature and annealing indicated that the crystal structures for samples prepared at 400 are better than others. FESEM images recorded from the surface of the annealed samples showed that the grain size is increased compared to before annealing. Also by annealing, average transmittance of the samples and the direct band gap are significantly reduced. Studies of the Al doped samples indicated that transmittance and crystallite size increase with Al concentration up to 3 wt.% and decrease with further increase in aluminum doping level to 7 wt.%.