The short-circuit durability of metal oxide semiconductor field-effect transistors (MOSFETs) has attracted much attention from various fields. The dynamic threshold drift problem of silicon carbide MOSFETs may cause changes in their short-circuit capability. A silicon carbide MOSFET short circuit testing platform was built to address this issue, and the changes in Class I short circuits of silicon carbide MOSFETs under different threshold voltage differences were studied. The article provides a detailed analysis of the working principle and short-circuit test results of the testing circuit. The experimental results show that the larger the threshold voltage, the greater the conduction resistance of silicon carbide MOSFETs, resulting in a larger short-circuit current and energy of silicon carbide MOSFETs.