The invention discloses a system and method for detecting the discharge type and the discharge capacity in a GIS, and belongs to the technical field of power transmission and transformation equipment.The system includes a solar blind filter system body, a single electron detector, a current/voltage conversion circuit, an ultra-high frequency sensor, an acquisition card and a processing device. The processing device receives a voltage signal and an electromagnetic pulse signal, and carries out discharge capacity measurement and discharge type identification in the GIS according to the voltagesignal and the ultra-high frequency electromagnetic wave signal. The system can achieve single-photon detection of internal discharge in the GIS, a detection wave band refers to the solar blind ultraviolet wave band, and the sensitivity and the reliability are high. The system and the method achieves the synchronous acquisition of an optical pulse signal and the ultra-high frequency electromagnetic wave signal, optical-electrical pulse sequence calculation and optical pulse counting are conducted through the processing device, and the discharge identification and calculation of the discharge capacity are then achieved.