The stationnary electric field of the DC gas-insulated metal-enclosed transmission line（GIL）basin-type in-sulator is distributed according to the electric conductivity of the dielectrics. Under long-term DC voltage

chargewill accumulate on the surface of insulator

leading to local electric field distortion and threatening the safe operationof the equipment. Therefore

it is of great necessity to study the phenomenon of surface charge accumulation in DCbasin-type insulator

by mastering accurate charge measurement techniques and charge inversed calculation algo-rithm

and surface charge accumulation characteristics

in order to provide reference for improving the insulationlevel of insulator. In this paper

a new type of surface charge measurement device for a basin-type insulator is devel-oped. The probe can be controlled to scan the surface of the insulator perpendicularly at an equidistant attitude. A setof concentric ring electrodes is used for the calibration of the electrostatic probe to obtain its spatial response func-tion. Based on the Cholesky decomposition method for matrix

the surface charge distribution of the insulator is in-versely calculated. The surface charge accumulation and decay characteristics of a ±200 kV DC pot insulators underdifferent DC voltages are experimentally studied. Based on the experimental and simulation results

the surfacecharge distribution models suitable for different conditions are proposed. This paper is of significance for further com-prehension of the surface charge accumulation phenomenon in DC basin-type insulators and for the amelioration ofcharge accumulation mechanism.