Aiming at the partial discharge abnormality in a 1 000 kV gas-insulated metal-enclosed switchgear (GIS), through the comprehensive application of multiple detection methods such as ultra-high frequency (UHF) and ultrasonic detection, and adopting a step-by-step troubleshooting strategy from overall to local and from out-side to inside, the precise location of the defect is successfully achieved, and the nature and specific location of the partial discharge are determined. To avoid the expansion of the defect, combined with the analysis of the partial discharge abnormal signals, correct maintenance measures are taken, and the faulty equipment is disassembled and replaced.