(Ba, Sr)TiO3(BST) thin films were prepared by pulsed laser deposition on the perovskite conductive oxide LaNiO3(LNO), YBa2Cu3O7−δ(YBCO) films, and Pt as a bottom electrode. The crystalline structures and surface microstructrue of the BST deposited on several substrates were characterized by x-ray diffraction measurement and scanning electron microscopy, respectively. The electrode effects on low-frequency dielectric behavior of BST thin films were investigated. The complex dielectric constants of the films were measured as a function of frequency in the frequency range from 0.1 Hz to 10 MHz. BST films grown on metallic oxide substrates exhibited marked dielectric relaxation below 10 MHz. This low frequency dielectric relaxations is attributed to the ionized space charge carriers such as the oxygen vacancies and cation defects in BST film, and the interfacial polarization in the grain boundary region and the electrode/film interface.