In Direct Current Gas Insulated switchgear (DC-GIS), surface charge accumulation on basin-type insulators can compromise their safe and stable operation. While surface modification is an effective method for suppressing this charge accumulation, traditional approaches that rely on uniform coatings struggle to adapt to the non-uniform electric field distribution on the insulator surface, which limits their effectiveness. Therefore, this paper proposes a partitioned modification strategy with a gradient design, where the surface is divided into zones based on the severity of charge accumulation to enable tailored modification. Firstly, the influence of voltage level, energization time and air gap size on charge accumulation characteristics is systematically studied. Based on these findings, the suppression strategy was explored by structurally dividing the insulator surface into three regions (A, B, and C) and applying functional coatings. The simulation results demonstrate that this partitioned scheme significantly suppresses charge accumulation. When the conductivity of region A was set to 6 × 10−18 S, the maximum surface charge density decreased by 23.19% compared to the uncoated state. The study confirms the effectiveness of the partitioned modification method, providing a reliable theoretical basis and practical reference for the charge suppression of high-voltage DC-GIS basin-type insulators.