Abstract: Gas insulated switchgear（GIS） equipment is subject to surface charge accumulation under DC or AC voltages in real operation, which could distort the electric field and incur flashover eventually. With the 3D high-resolution surface charge measurement system established on the actual 220 k V GIS basin insulator, the present research captured the surface charge distribution characteristics of the insulator under DC and AC voltage with high precision by the probe scanning on the insulator surface. The experiment results show that: 1) Surface charge demonstrated obvious polarity effect under DC voltage. Under positive DC voltage, there accumulated mainly positive surface charges, while under negative one, the polarity of accumulated surface charge was all negative. Whatever the polarity of accumulated surface charge is, as the amplitude of applied voltage increased, the amount of accumulated surface charges mounted up and with the voltage application prolonging, the average value of surface charges kept increasing until it reached saturation. 2) Accumulated in the context of AC voltage were mainly negative surface charges with less density compared to the DC scenario. As the amplitude of applied AC voltage grew, the amount of accumulated homogeneous surface charges firstly increased, then decreased, and finally reached saturation. Above all, the insulating issues occurred by the surface charge accumulation require due attention in the application and maintenance of GIS equipment, and the research in this paper can provide a reference for the optimal design of GIS/GIL insulators.