Gas insulated switchgear（GIS）and gas insulated metal-enclosed transmission line（GIL）have large operating currentand obvious temperature gradient distribution inside the equipment

intensifying thecharge injection and the migration near high voltage electrode

causing the charge accumulation in the space and surface of insulator

distorting the electric fieldandeasily inducing flashover along the surface.To this end

a charge injection and accumulation model in a DC insulating spacer under electrical-thermal coupling stress is set up

the space charge and surface charge accumulation of the insulator considering the charge injection and migration characteristics is considered and the surface electric field distribution of the insulator under different load currents is analyzed.The research results show that under temperature gradients

charge injection at the conductor-insulation interface will cause the accumulation of space charges of the same polarity inside the spacer

and the accumulation density of space charges will increase with the increase of load current.The accumulation of space charges can weaken the electric field intensity near the high-voltage electrode

enhance the normal electric field intensity on the convex side of the spacer and intensify the accumulation of surface charges.The accumulation of space and surface charges increases the surface potential of the spacer

resulting in an increase of the potential difference near the ground electrodeand a significant increase in electric field strength.The field strength at the three junctions of the ground electrode is increased 103%

namely from 1.71 kV/mm at no-load conditions to 3.47 kV/mm under the action of rated current.The research results are helpful to understand the mechanism of surface electric field distortion of DC insulating spacer under temperature gradientand have certain reference for the optimal design and safe operation of DC insulating spacer.