Abstract: As a commonly used low molecule interface modification agent, the interfacial compatibility of coupling agent is easily affected by plasma. To further improve the interface properties between fillers and epoxy resin, nanosilica is coated with macromolecular chains by carboxyl-terminated hyperbranched polyester. Then Fluorination Grafting of Fillers by Low-temperature ions. The chemical composition, microscopic morphology, charge characteristics and surface flashover characteristics of epoxy composites under different modification methods are tested and analyzed. The experimental results indicate that comparing with the coupling agent pretreatment, the nanosilica modified by hyperbranched surface grafting has a better interfacial compatibility with the epoxy matrix, and the agglomeration size in epoxy matrix is significantly reduced compared with KH550/fluorination modification. Doping 3% CHBP/fluorination modified fillers can effectively reduce the average charge density of epoxy composites under high-voltage electric field, and inhibit space charge accumulation and cross-interface transport. The flashover along the surface is effectively suppressed, and the dispersion of flashover voltage also reduced. The maximum value of the breakdown field strength reaches 40.88kV/mm, which is 12.34% and 20.13% higher than that of CHBP modified and KH550/fluorination modified samples with the same mass fraction, respectively. As a feasible and effective method, the grafting of fillers with fluorinated modified polymer additives provides a new research idea for filler modification.