To ensure the safety and reliablity of silicon carbide (SiC) power devices in the overload, short circuit and other conditions, the short circuit mechanism of SiC devices must be fully understood. Firstly, the mechanism of short-circuit current is analyzed in detail under hard-switching fault. Then, the influence of different circuit parameters on short circuit characteristics of SiC MOSFET is analyzed and compared. The key factors influencing the short-circuit characteristics are further revealed, and the short circuit capacity and device deterioration mechanism of Si and SiC MOSFET are compared and analyzed. The paper provides a guidance for designing short-circuit protection circuit of SiC MOSFET to some extent.