In order to analyze the discharge features of different insulation defects in various experimental conditions, according to characteristics of partial discharge (PD) from the insulation defects in gas insulated switchgear (GIS)) and using ultra high frequency (UHF) method, a lot of PD experiments are carried out based on the designed four typical physical models of insulation defects of GIS in the simulation device, and the real samples of UHF PD waveforms are recorded. The features of UHF PD waveforms in the different situations are discussed and analyzed in detail, which include different sizes or positions of the physical models or under the different voltages and so on. The results show that in low voltage, regardless of types of UHF electromagnetic wave excited by PD sources, the shapes of PD waveform changed little before the changes of waveform. The remaining time is about several nanoseconds.