The invention discloses a supersonic online detection system of a 1000kV GIS, and relates to the field of electronic technology. Supersonic probes are mounted on a casing or basin-type insulator of the 1000kV GIS, and collect internal discharge signals of the GIS in real time, the signals are transmitted to an optical relay station via fibers and converted into electric signals, the electric signals are amplified, processed and stored, and then analyzed by a host computer, and display, printing and teletransmission functions are provided. The supersonic online detection system of the 1000kV GIS can be applied to the field in detecting partial discharge defect of the common 1000kV GIS, the problems as inaccurate positioning and slow response of a traditional detection method are effectively solved, and the system of the invention is worthy of popularization and use widely.