In case of applying DC voltage

a large amount of charge will accumulate on the insulating spacer of gas insulated switchgear (GIS)

which will greatly reduce the flashover voltage along the surface

resulting in a series of faults of electrical equipment. Based on the above problems

the source and conduction path of the insulating spacer surface charge is analyzed in this paper

the two-dimensional axisymmetric simulation model is constructed and the relevant parameters are set by using finite element simulation calculation method

and the influence of voltage polarity

different voltage amplitudes and voltage polarity reversal on the distribution of insulating spacer surface charge is studied. The results show that under DC voltage

the charge which is oppotite to the applied DC voltage polarity is mainly accumulated in the concave side and the charge which is identical to the DC voltage polarity is mainly accumulated in the convex side and the charge density accumulated on the concave side is larger. In case of DC voltage at -100 kV after polarity reversal

the charge density originally accumulated on the surface of the insulating spacer shows a trend of increasing firstly and then decreasing gradually

and then the polarity is converted to reach saturation. The distortion degree of the electric field near the high voltage end and from 0-20 mm along the surface of the insualting spacer is obvious. The peak value of the electric field appears before variation of the surface charge polarity of the insualting spacer. Compared with the saturated state of the charge

the maximum field strength of the concave side of the insulating spacer is increased by 46%

and that of the convex side by 5.4%. This study can provide guidance for the distribution of the surface charge of the insulating spacer under DC voltage.