Abstract: Taking an oil-leakage and heating defect in a 110 kV bushing-type cable terminal as the research object, combining it with live detection technology, this study eliminates the possibility that the defect is caused by the material itself through disassembly inspection and stress cone material detection. Based on the terminal structure and the mechanisms of oil-leakage and heating, the causes of the oil-leakage and heating defect are systematically analyzed. The study reveals that the root cause of the defect is poor lead sealing workmanship, which leads to moisture ingress into the cable. During long-term operation, partial discharge is generated, resulting in ablation and cracks on the stress cone, and ultimately causing the oil-leakage and heating of the terminal. In view of this problem, preventive measures are put forward, including strengthening the full-life cycle management of equipment and deepening the application of live detection and online monitoring technologies, which provide an important technical reference for the construction quality control and operation management of high-voltage cables.