Barium strontium titanate (Ba0.66Sr0.34TiO3) thin films and seed-layers were deposited on the Pt/Ti/SiO2/Si substrate by R.F. magnetron sputtering method. Effects of the substrate temperature on electrical properties of BST thin films were studied. The effect of seed-layer was also studied. From the XRD results, we could confirm that the seeding layer of BST thin film plays a key role in lowering the crystallization temperature of BST thin films. When seed-layer was inserted between BST and Pt, the crystallization of the BST thin films was considerably improved and the processing temperature was lowered. Compared to the pure BST thin films, dielectric constant, dielectric loss, and leakage current of BST thin films deposited on the seed-layer were considerably improved. It could be revealed that electrical properties are influenced by the substrate temperatures of BST thin films and are enhanced by the seed-layer.