Abstract: An analysis was carried out on the burst failure of an epoxy bushing at the cable terminal of a 220 kV outdoor gas-insulated metal-enclosed switchgear (GIS). The research delved into the effects of an extremely cold environment following a sharp temperature decline on the bushing’s performance. Employing technical methods such as macroscopic inspection, penetrant testing, and mechanical property testing, taking operational environment, material properties, and structural factors into account, and referencing test results of spare bushings, causes of the accident were thoroughly examined from multiple dimensions. It was discovered that minor cracks existed at the bonding interface between the insert and resin in the spare epoxy bushing. The findings revealed that improper process control during the curing phase led to the formation of microcracks between the resin and insert in the epoxy bushing. In combination with mechanical vibrations, the resin underwent accelerated degradation under the influence of light, heat, moisture, and industrial pollution. In the extremely cold environment after a rapid temperature drop, axial displacement and end rotation of the GIS long busbar enclosure increased dramatically. The rapid propagation of these cracks resulted in bushing cracking, subsequently triggering surface discharge along the inner wall of the bushing. Under the combined effect of short-time fault current and arc voltage, the terminal bushing finally exploded.