Abstract: To compare sensitivity of partial discharge detection for GIS between UHF and ultrasonic method, a partial discharge detection platform for 220kV GIS is built based on real GIS equipment. Five cases of partial defect (PD) discharges are simulated, and their values under different voltage level are measured by using of UHF and ultrasonic method. At the same time, such values as initial discharge voltage, average apparent discharge magnitude, discharge times and discharge amplitude, are compared. It can be seen from results that, 1) UHF method show higher sensitivity in detecting the five types of partial discharges; 2) ultrasonic method is sensitive in detecting partial discharges caused by free metallic particles on insulator, mental sharps on inner shell of insulator, and floating electrode on high voltage conductors, but its sensitivity is lower than that of UHF method. Therefore, it is suggested that UHF should be used as major method to detect and diagnose inner defect in GIS, and ultrasonic method as assist detect measure.