We report for the first time Ba0.6Sr0.4TiO3(BST 60/40) thin films with Mg additive fabricated by Metalorganic decomposition technique on platinum coated silicon substrates using acetate-alkoxide precursors.[1]The structural and electrical properties of the BST thin films were greatly changed by additions of Mg. The surface morphology of the films was smooth with a dense microstructure. The typical small signal dielectric constant and the loss factor for a 0.4 μm thick undoped BST films were 450 and 0.013, respectively, at an applied frequency of 100 kHz. The dielectric loss was significantly reduced by the Mg content. The tunability (ΔC/C0) was found to change from 20.7% to 5.8% as the Mg additive content was changed from 0 to 20 mol%. The films exhibited high resistivity of the order of 1012Ω-cm even up to an applied electric field of 100 kV/cm.