In recent years, the influence of filler surface groups in epoxy resin coatings on the protective performance of coatings has attracted widespread attention. This study uses silane coupling agents to modify silicon carbide fillers, grafting hydrophilic and hydrophobic groups on their surfaces and studying the corrosion resistance and wear resistance of composite coatings under harsh environments. Meanwhile, density functional theory was used to analyze the electronic properties of the epoxy resin matrix as well as the binding sites with silicon carbide fillers. Molecular dynamics simulation was used to investigate the barrier properties of different types of silicon carbide fillers and resin coatings. The experimental and simulation results jointly indicate that the epoxy composite coating with the hydrophilic modified silicon carbide filler has better anticorrosion and wear resistance. Overall, this study provides a theoretical basis for the practical application of surface functional groups of fillers to the protective performance of coatings.