Abstarct: In this thesis we have studied the morphological, structural and optical properties of pure tungsten oxide (WO3) samples grown by spray pyrolysis and thermal evaporation methods. For these characterizations we have used field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), UV-Vis spectroscopy and photoluminescence (PL), respectively. In the grown samples by spray pyrolysis method, ammonium tungstate solutions, using pure tungsten oxide powder (99.9%), have been used. Variable parameters are including: substrate temperature (300-350-400 and 450 ° C), spray rate (1, 5 and 18 ml/min), annealing temperature (450 and 500 °C), substrate type (glass, silicon and FTO), molarity of the solution (0.01, 0.03 and 0.05 M), volume of the solution (10, 30 and 50 ml) and finally the effect of adding methanol as a solvent. FESEM images of the samples indicate the formation of nanoparticles, nano and micro wires and fairly regular intertwined strings. The XRD patterns indicate that the structures of samples are in amorphous and polycrystalline phases. Transmission spectra of the samples indicate that all the grown samples are transparent in the visible range with an indirect band gap of about 3.5 eV. In samples grown on silicon wafer by thermal evaporation method, nano-structures of pure WO3 are grown using WO3 powder (without catalyst or additive) in the presence of oxygen gas. In this work we have investigated the influence of the distanance between the substrate and boat. FESEM images indicate the formation of the grains and micro-rods with nanometer diameters (~400 nm) in monoclinic phase. PL spectra of the samples shows two main peaks in the ultraviolet (due to band to band transition) and the blue region (due to crystal defect transitions) at room temperature.