Abstract: To fabricate high-performance polymer-based electrothermal composites, graphite film with high thermal conductivity and electrothermal conversion efficiency was used as a functional filler. Firstly, The graphite film was functionalized through a dopamine-silane coupling agent treatment, followed by the construction of a thermally conductive network structure of functionalized graphite film. Finally, the functionalized graphite film was incorporated into epoxy resin to fabricate high thermal conductivity graphite film/epoxy composites with electrothermal conversion function. The modification mechanism of graphite film was characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectra (FTIR), X-ray Diffraction (XRD) and contact angle measurements. The results indicated that dopamine covalently bonded to the graphite film surface, providing reactive sites for the grafting of silane coupling agents. The surface morphology of the modified graphite film changed, but its phase structure remained unaltered, and the compatibility with epoxy resin was enhanced. The thermal conductivity and electrothermal conversion performance of the graphite film/epoxy composites were systematically investigated by thermocouples, infrared thermal imaging, thermal conductivity measurements, and ice-melting tests. The results revealed that the constructed network structure endowed the composites with superior thermal conductivity, which was further enhanced by the modification and increased content of graphite film. Notably, the composite with 31.9wt% modified graphite film exhibited a high thermal conductivity of 7.14 W·(m·K)⁻¹. Under a voltage of 12 V, the surface temperature of the composite could rapidly increase from room temperature to 120℃ within 80 s and completely melt an ice cube within 60 s, demonstrating its excellent electrothermal conversion capability.