Gallium nitride technology is becoming more popular nowadays and has been widely used to further improve the performance of power converters. As one of the most accessible GaN devices, cascode GaN devices have several advantages. The cascode GaN device is easier to manufacture and the reliability is improved in the semiconductor aspects. However, the short circuit capability has not been deeply studied and the performance degradation after short circuit remains unknown. In this paper, short circuit (SC) tests under different conditions are carried out and the comparison with traditional GaN devices is presented. Finally, the performance degradation after SC test is presented.