Polymers and fillers with high dielectric constant (εr), charge-discharge efficiency (η) and breakdown strength (Eb) are fundamental to the development of nanocomposite dielectrics for superior energy storage capabilities. Herein, high-εr P(VDF-TrFE) is used to prepare the P(VDF-TrFE)-g-PMMA matrix with elevated εr and η, then the P(VDF-TrFE)-g-PMMA/BNNS-NH2 nanocomposites with uniformly oriented distribution of h-BN is obtained by a squeegee casting process using amino-boron nitride (BNNS-NH2) as fillers. Thanks to the limiting effect of PMMA and the high insulating effect of BNNS-NH2, the energy storage density (Ue) of the nanocomposite is up to 15.1 J/cm3 at 500 MV/m, which is 358 % and 182 % of the original P(VDF-TrFE). Furthermore, the η could reach to 72 %, being 184 % of neat polymer. These results demonstrate that the coordinated enhancement of Ue and η is critical for high performance energy storage, which provide scientific and technological support for the practicability of PVDF-based dielectrics.