Abstract: As a common insulating material, epoxy resin under high-voltage direct current electric field is prone to accumulate charges on its surface, causing electric field distortion, resulting in a decrease in the insulation performance of the material and affecting the reliability of the power system. To improve the charge characteristics and insulation properties of the gas-solid interface, based on the atmospheric pressure plasma jet technology, plasma gradient silicon deposition were conducted on the epoxy resin surface. The surface physical and chemical properties, surface conductivity, surface charge dissipation and creeping pressure characteristics of epoxy resin before and after modification were measured by multiple parameters. The experimental results show that the gradient modification has a significant effect on the physical morphology and chemical composition of the material surface. The conductivity of different regions has achieved a gradient distribution, which speeds up the dissipation of surface charges and reduces the surface trap energy level; The flashover voltage of the subsequent samples can increase by 30.16% along the surface. In summary, the plasma surface gradient silicon deposition treatment can improve the electrical properties of the epoxy resin surface, and has broad application prospects in the insulation design of high-voltage DC equipment.