Strontium barium niobate thin film was successfully deposited on MgO(001) substrate with the sol gel process, the film thickness was up to 5 μm. The film microstructure was studied by the methods of X ray diffraction, X ray rocking curve,  scan, as well as Raman scattering spectroscopy. The results show that the SBN thin films have the (001) preferred orientation, and the SBN tetragonal phase with enhanced (001) orientation were observed in thicker films. A very large value of 6.62×10 -11 m/V of effective transverse electro optical coefficient for the SBN film deposited on transparent fused silica substrate was measured.