The invention relates to a GIS partial discharge optical ultrahigh frequency combined detection method. The method is characterized in that the method comprises the following steps: 1), placing a photomultiplier at the position of an observation window of GIS; 2), placing an external-type ultrahigh frequency sensor close to a basin-type insulator of the observation window at step 1); 3), carrying out the simultaneous detection through the photomultiplier at step 1) and the external-type ultrahigh frequency sensor at step 2), and determining whether partial discharge happens in an air chamber where the observation window is located according to a detection result. The try-out proves that the method gives full play to the advantages that the optical detection anti-interference performance is high and the ultrahigh frequency detection range is large, and can achieve the accurate on-site detection of partial discharge of the GIS.