Abstarct: In this experimental research the morphological, structural and optical properties of Molybdenum trioxide (MoO3) samples prepared using spray pyrolysis and hydrothermal methods were studied. Also the effect of Sn as a dopant on MoO3 samples prepared by spray pyrolysis method was investigated. Samples were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and UV-Vis spectroscopy. The growth parameters have been studied using spray pyrolysis method are as following: substrate temperature (in the range of 250-450 ℃), concentration of precursor solutions (limited to 0.01-0.1 M), volume of precursor solutions (in the range of 25-75 mL), spray rate (limited to 5- 20 mL/min) and the effect of addition of Sn as a dopant on the samples with different molar ratio [Sn/Mo] (in the range of 0.05-0.50). The XRD pattern shows the thermodynamically stable orthorhombic α-MoO3 for that pure samples. The strong reflection peaks (0k0) with k=2, 4, 6 have seen in patterns proves the existence of the lamellar structure. The FESEM images of samples show the formation of micro-spheres which their shell was shaped in lamellar structure. Transmittance, absorption coefficient and direct band gap of samples obtained and analyzed. In the hydrothermal technique sprayed seed laxyer was used for growing nanostructured thin films. In this case the effect of different substrates, which have been grown by spray pyrolysis with different conditions, and the effect of time of hydrothermal reaction were studied. The XRD pattern shows the formation of orthorhombic α-MoO3 structure, and the FESEM image illustrates the preferential grows on the substrate.