Inorganic/polymer nanocomposites, using one-dimensional (1D) core-shell structure BaTiO3@Al2O3 nanofibers (BT@Al2O3 nfs) as fillers and poly(vinylidene fluoride) (PVDF) as the polymer matrix, have been prepared. The core-shell structure BT@Al2O3 nfs have been synthesized via coaxial electrospinning. The breakdown strength (E-b) and discharged energy density of the nanocomposites can be significantly improved by creating an insulating Al2O3 shell layer with moderate dielectric constant on the surfaces of BT nanofibers to form a moderate interfacial area. The Al2O3 shell layer could effectively confine the mobility of charge carriers, which reduces energy loss by reducing the Maxwell-Wagner-Sillars (MWS) interfacial polarization and space charge polarization between the fillers and the polymer matrix. As a result, the nanocomposite films filled with 5 vol% BT@Al2O3 nfs exhibit a excellent discharge energy density of 12.18 J cm(-3) at 400 MV m(-1), which is approximate to 254% over bare PVDF (4.8 J cm(-3) at 350 MV m(-1)) and approximate to 1015% greater than the biaxially oriented polypropylenes (BOPP) (approximate to 1.2 J cm(-3) at 640 MV m(-1)). The work here indicates that this promising state-of-the-art method of preparing high energy density nanocomposites can be used in the next generation of dielectric capacitors.