The 0.9Pb(Sc0.5Ta0.5)O3–0.1PbTiO3/0.55Pb(Sc0.5Ta0.5)O3–0.45PbTiO3 multilayer thin films ((PSTT10/45)n, n=1–6, 10) are deposited on SiO2/Si(100) substrates by radio frequency magnetron sputtering technique with LaNiO3 buffer and electrode layer, and the films are subsequently annealed by a two-step rapid thermal approach. It is found that the interfacial density of the film has an important influence on the electric property of the film. The electric property of the film increases and reaches its critical point with the increase of interface density, and then decreases with the further increase of the interface density. With an interfacial density of 16 μm?1, the film shows an optimized dielectric property (high dielectric constant,εr=765, lowest dielectric loss, tanδ=0.041, at 1 kHz) and ferroelectric property (highest remnant polarization, 2Pr=36.9 μC/cm2, low coercive field, 2Ec=71.9 kV/cm). The possible reason for the electric behavior of the film is the competition of the interface stress with the interface defect.