The invention relates to the field of gas insulated metal-enclosed switchgear (GIS) partial discharge monitoring, in particular to a GIS partial discharge signal source and a method for simulating partial discharge. The GIS partial discharge signal source comprises an oscilloscope or collecting device and further comprises a computer and a partial discharge signal source body, wherein the computer is in communication connection with the partial discharge signal source body; the partial discharge signal source body comprises a master control module and a storage module, a pulse signal transmitting module, a display module and a synchronization module which are connected with the master control module; the synchronization module is connected with the oscilloscope or collecting device. The GIS partial discharge signal source has the advantages that the problem that a traditional pulse-current-method signal source is easily filtered by an ultrahigh-frequency filter which takes the traditional pulse-current-method signal source as interference due to the fact that the traditional pulse-current-method signal source is quite low in frequency band is solved, and the problem that a signal generator type signal source can be only applicable to researches such as ultrahigh-frequency partial discharge propagation characteristics and discharge quantity calibration and cannot simulate different insulation defect partial discharge signal sources; whether the multiple GIS ultrahigh-frequency detecting systems of a power grid company work normally or not can be checked.