Abstract: The surface charge accumulation on the basin-type spacer significantly affects the electric field distribution and the flashover in the direct current gas insulated transmission line (DC-GIL). Therefore, it is of great significance to investigate and regulate the surface charge distribution on the spacer, thus improving the electric field distribution. Based on the experimental platform of a downsized DC-GIL, the influences of different nonlinear conductivity coatings (mass fraction of SiC: 23.1%, 37.5% and 47.4%) on the surface charging and discharging behaviors of the basin-type spacer were studied under different conditions, i.e., DC, metal particle, and polarity reversal operation. Results show that the surface charge polarity on the epoxy/Al₂O₃ spacer depends on the competition result between the bulk conduction and the gas conduction, which is significantly field-dependent. The surface nonlinear conductivity (SNC) spacers can adaptively regulate the surface charge and the electric field distributions, thus improving the flashover voltages under different operation conditions. This study provides a potential solution for developing novel DC-GIL spacers with high reliability.