Epitaxial Ba 0.65 Sr 0.35 TiO 3 thin films were successfully deposited on Pt?MgO(100) substrates by sol gel techniques. XRD patterns demonstrated that(001) planes of BST films were mainly oriented parallel to Pt(100) and MgO(100). SEM results showed that the surface of BST thin film was smooth and free of cracks, and the film thickness was 260nm. The average grain size of the films was about 48.5nm. The dielectric constant and dissipation factor for Ba 0.65 Sr 0.35 TiO 3 thin film at a frequency of 10kHz were 480 and 0.02, respectively. The temperature dependence of dielectric constant exhibited sharp Curie transitions at temperatures around 35℃. The leakage current density of a BST film on Pt?MgO was 1.5×10 -7 A?cm 2 at an applied voltage of 3V. Such epitaxial Ba 0.65 Sr 0.35 TiO 3 thin films are the excellent materials for preparing uncooled infrared focal plane arrays.