Abstarct: In this thesis, the structural, optical and morphological properties of titanium dioxide TiO2, magnesium oxide (MgO), TiO2 / MgO nanocomposite and TiO2-MgO core-shell with three different ratios of core/shell 0.5:0.25, 0.5:0.5 and 0.5:0.75 prepared by sol-gel method were studied. Initially, the titanium dioxide sample was synthesized and annealed at two different temperatures. The results of the X-ray diffraction pattern showed that with increasing the annealing temperature, the phase changes and the size of the crystallites increases. Investigation of the optical properties showed that the band gap of the samples decreases with increasing the annealing temperature. The X-ray diffraction pattern of magnesium oxide showed that it has a periclase cubic phase. The study of optical properties of this sample indicated that the band gap is equal to 5.41 eV. The x-ray diffraction patterns of the core-shell structures revealed formation of a cubic structure of magnesium oxide and the tetragonal structure of titanium dioxide (anatase phase). The average crystalite size of the samples increases with increasing shell thickness. Studying the optical properties of the core-sell samples showed that the band gap decreases with increasing the shell thickness.