To ensure the reliability and safety of GaN High Electron Mobility Transistor (GaN HEMT) power devices operating at high temperature, high frequency and high voltage, it is important to study the short circuit protection methods of GaN HEMT power devices. This paper proposes a short-circuit detection method based on gate leakage charge for GaN Metal-Insulator-Semiconductor HEMT (GaN MIS-HEMT). During a short circuit fault, a rapid spike in junction temperature can cause a gate leakage current in the gate loop. The proposed method is immune to parasitic parameters caused by the package and PCB layout, and can realize short-circuit detection within 1 μs. With the increase of the short-circuit bus voltage and ambient temperature, the short-circuit detection time can be shorter, which is more suitable for high-temperature, medium and high voltage applications.