BST thin films were prepared with various deposition conditions by rf-magnetron sputtering. As substrate temperature increases and Ar/$O_2$ratio decreases, the electrical properties of the BST films improve. The conventional Schottky model and modified-Schottky model were introduced in order to investigate the leakage-current-conduction mechanisms of the deposited films. It was found that the modified-Schottky model better describes the current-conduction mechanism in the BST films than the conventional Schottky model. From the modified-Schottky model, optical dielectric constant ($varepsilon$), electronic drift mobility ($mu$), and barrier height $({phi}_b)are calculated as $varepsilon$=4.9, $mu$=0.019 $ extrm{cm}^2$/V-s, and ${phi}_b=0.79 eV.