Gas-insulated metal-enclosed switches（GIS）are widely used in power systems. Among them

basin-typeinsulators have been subjected to aging degradation under the effect of electro thermal stress for a long time

and seri-ous accidents may be caused in severe cases. Aging degradation of basin-type insulator is actually a chemical reac-tion process

so it is of great importance to study the thermal decomposition process of basin-type insulator. Based onthe principle of thermal analysis

the thermal decomposition process of the basin-type insulator under five differentheating rates is analyzed by TG method. The activation energy of the basin-type insulator is calculated by the Flynn-Wall-Ozawa method and the Kissinger method. The results show that the calculated results by the first method of Fly-nn-Wall-Ozawa method and Kissinger method are basically the same. The activation energy calculated by the secondmethod of Flynn-Wall-Ozawa method initially increases with the increase of conversion rate. Peak at a conversionrate of 0.12

then decrease slightly as the conversion rate increases and last gives a microscopic explanation of thisphenomenon. The above research has certain guiding significance for accurately calculating the activation energy ofthe basin-type insulator

revealing the aging mechanism and evaluating the aging degree.