Disc insulator is widely used in gas insulated station（GIS） equipment

which is an important part of the electrical isolation between central conductors and a grounding flange. We analyzed the insulation performances of materials used in the disc insulator. The heating curve of the disc insulator was obtained by using the theoretical model

and an insulation accident was analyzed using this curve. The electric and thermal field distribution of the disc insulator was obtained through the electro-thermal coupling analysis process

and the relationship between the hot-spot temperature and the current load was calculated. The research results show that the insulating properties of the spacer material have significant nonlinear relationship with temperature. The eddy current field and harmonic field analysis method by finite element method（FEM） can effectively calculate the heat of center conductors and a spacer under 50 Hz condition. The maximum electric field strength locates at the interface of center conductors and a spacer with value of 6.033 MV/m

and the hot spot is near center conductors of a spacer with value of 82 ℃. When the load is higher than 1.5 times of the rated value

the sudden rise of temperature will appear which is called thermal collapse phenomenon. Therefore

the thermal and electric field coupling calculation process provides a way to check the performance of the design scheme of the disc insulator

and can also provide a theoretical guidance for the field maintenance and accident analysis of disc insulators.