Abstract: Dielectric energy storage materials with high working field strength and high energy storage efficiency have an important impact on improving the performance of power equipment and reducing the volume of power equipment. The cubic SrTiO₃ powder was prepared as ceramic filler by the mixed alkali method, and the surface of the cubic SrTiO₃ particles was treated by polyvinylpyrrolidone (PVP) surface modification. The uniform polyvinylidene fluoride (PVDF) flexibility composite was prepared by the casting method. The effect of surface PVP modified cubic SrTiO₃ filler on the dielectric properties and energy storage density of PVDF dielectric composites was systematically studied. The results show that the morphology of the SrTiO₃ powder is cubic and the size is 200-400 nm. The particle size distribution is relatively uniform. The PVP coating layer formed on the surface of the cubic SrTiO₃ filler can effectively prevent the agglomeration of the cubic SrTiO₃ filler in the PVDF composites. At the same time, the PVP coating layer can improve the dispersion and bonding of the cubic SrTiO₃ filler in the PVDF polymer. PVDF dielectric composite has excellent dielectric properties and breakdown strength. The dielectric constant of PVDF composites increases with the increase of the filling amount. When the filling amount of cubic SrTiO₃ filler is 40vol%, the dielectric constant of the composite is 34.9. The energy storage density of PVDF dielectric composite increases first and then decreases with the increase of the filling volume. When the filling volume of the cubic SrTiO₃ filler modified by the surface PVP is 5vol%, the energy storage density of the composite reaches 5.3 J/cm³.