The utility model relates to a GIS partial discharge online monitoring calibrator, which comprises a pulse signal source and a transmitting antenna, wherein the pulse signal source can send an analog signal source, and the transmitting antenna is connected with the pulse signal source and injects the analog signal source into a GIS cavity. The calibrator can check the sensitivity of a partial discharge UHF (ultra high frequency) detection device under test in detecting injection signals on line based on an ultra high frequency method. The GIS partial discharge online monitoring calibrator is simple in structure and convenient to operate.