The amorphous PbO-{{{{ { {Bi }_{2 }O }_{3 } }}-{{{{ { { B}_{2 }O }_{3 } }}(PBB) layer was deposited on the ({{{{ { {Ba }_{0.5 }Sr }_{0.5 } }})TiO3 (BST) film using r. f mag-netron sputtering and diffused throughout the film after the annealing at $650^{circ}C$ The effect of PBB phase on the dielectric properties of the BST film was investigated. The PBB phae in BST film was identified by an energy dispersive spectroscopy (EDS). Dielectric properties of BST film were significantly improved after the diffusion of the PBB. The leakage current density of the BST films was 9.9$ imes${{{{ {10 }^{-6 } }}A/cm2 and BSt film with PBB was 1.0-3.3$ imes$10-7A/cm2 at 1.25V and the dielectric constant of BST film with PBB was in-cerased to 533 at zero voltage. From these I-V and C-V characteristics the formation of insulating metal ox-ide in the ferroelectric thin film also improved the dielectric properties of the film,