Abstract: The carbon shell was coated on the surface of ferroferric oxide via high temperature carbonization to form the core-shell structure of Fe₃O₄@C. Compared with the single structured filler particles, the core-shell structure of Fe₃O₄@C was more uniform and more compatible with the organic matrix. Thus, the Fe₃O₄@C/PVDF (Polyvinylidene fluoride)flexible film with high dielectric constant and low dielectric loss was obtained. Carbon shell plays a key role in improving the dielectric properties of materials. The carbon shell can not only be used as a transition layer between the Fe₃O₄ core and the PVDF matrix, but also strengthen the interfacial polarization of the material. The improvement of the dielectric properties of the materials is mainly based on percolation theory and interfacial polarization theory. According to the experiment, the percolation threshold of Fe₃O₄@C was 12%. During the experiment, it is necessary to accurately control the amount of added filler. At this packing ratio, the film was filled with countless microcapacitors and the dielectric constant of the material was increased rapidly. At the same time, the interfacial polarization of the electric dipole between different interfaces further enhanced the dielectric properties of the material. Compared with pure PVDF, carbon fiber/PVDF and graphene oxide (GO)/PVDF, the Fe₃O₄@C/PVDF flexible film prepared in this paper has a higher dielectric constant of 115 (normal temperature, 1 kHz) and lower dielectric loss of 0.063. Meanwhile, compared with pure PVDF, its tensile strength was increased from 42.3 MPa to 76.6 MPa, and the elasticity modulus was increased from 1.3 GPa to 2.0 GPa. Thus, the prepared materials can be used as a flexible film with high dielectric in electronic components and other fields.