MgO thin film was deposited on soda lime glass substrate by sol-gel process. MgO thin film with the (200) preferred orientation were prepared by heat-treated at 300~500°C for 10 min. The crystallization, microstructure and electrical properties with various parameters of MgO thin films were investigated. Consequently, it was shows that the (200) preferred orientation of MgO thin film could be obtained as the heating temperature was increased. At heating temperature of 500°C, MgO thin film was composed of columnar crystals with a size of 120 nm. The dielectric constant of the (200) preferred orientation of MgO thin film at 1 kHz without the electric field was 7.2, with a dissipation factor of 4%. When the electric field was increased, the dielectric constant approaches to 7.9 with the dissipation factor of 2.1%. The refractive index of MgO thin film depended on the film thickness. The refractive index of 250 nm thickness was 1.70.