Abstract: Barium titanate (BT) nanoparticles loaded reduced graphene oxide (RGO-BT) was prepared through a solvothermal method, and the diameter of BT was 20~30 nm verified by transmission electron microscope. Precursor of tert-butyldimethylsiyl chloride (TBS) terminated PBO (TBS/prePBO) was synthesized by a condensation polymerization of paraphthaloyl chloride with 4, 6-diaminoresorcinol dihydrochloride (DAR) protectively pretreated by TBS. PBO doping with RGO-BT (RGO-BT/PBO) ternary composite films were prepared by a solution casting and stepwise heating cyclization treatment. Studies showed RGO-BT/PBO could improve tensile strength and Young's modulus compared with PBO. When the mass fraction of RGO-BT was 10%, the tensile strength and Young's modulus increased by 84% and 200%, respectively. Dielectric performance of composite was greatly improved by a synergistic effect of high dielectric constant of BT and interfacial polarization of graphene nanosheets. When the mass fraction of RGO-BT rose up to 10%, the dielectric constant of composite reached as high as 42.77 which was nearly 15 times larger than that of pure PBO polymer and had a good stability (47.38-41.63) in a wide frequency range of 10¹-10⁴ Hz.