Abstract: SiC/Si cascode device, formed by low-voltage Silicon Metal-Oxide-Semiconductor Field-Effect Transistor (Si MOSFET) and Silicon Carbon Junction Field-Effect Transistor (SiC JFET), has several advantages such as low driving-voltage of Si MOSFET, high blocking-voltage, and low loss of SiC JFET. In this paper, the effect of low-voltage Si MOSFET on the short-circuit performance of SiC/Si cascode device has been investigated with experiment and numerical simulation. The results give that during the short circuit, the highest temperature of SiC JFET in the cascode case is lower than that of single SiC JFET case, so the short-circuit failure duration of SiC/Si cascode device is longer than that of single SiC JFET. Moreover, with the increasing in the rated voltage of Si MOSFET, the short-circuit failure duration for SiC/Si cascode device also increases.