Low energy electron diffraction (LEED) have been applied to investigate the surfec structure of transition metal oxides BaTiO3(111) (√3x√3)R30° and CoO/Ag(100) systems. The kinematic (SPA-LEED) method was used to investigate the structure and morphology of CoO thin films growth on Ag(100) substrate. The dynamic method (Tensor LEED) was used to quantitatively analyse the intensity spectra of LEED spots in order to extract the detailed surface crystallographic information. By a tensor LEED analysis of the clean Ag(100) surface. A small inward relaxation in the top layer of Ag(100) surface was found and the surface structure parameter of Ag(100) were refined. For a 4 ML CoO/Ag(100), expansion in first and second layer were found. In addition, the first layer shows surface rumpling. For a 1.2 ML CoO/Ag(100), the precursor super structure is determined. CoO(111) (√3x√3)R30° superstructure with 30° rotated domains as well as CoO(100) (2 1) superstructure has been observed on a 10 ML CoO film. Strain relaxation of CoO films was found to be at abour 5-6 ML. The BaTiO3(111) (√3x√3)R30° reconstructed surface has been analyzed by the tensor LEED method. The surface shows a BaO termination with one third of O vacancies on the topmost layer.