Featuring the excellent material properties, SiC power devices become the most promising power devices in high-temperature and high-power applications. Nowadays, with breakthroughs in high-temperature packaging techniques, thermal runaway becomes the new bottleneck limiting high-temperature applications of SiC devices. To address this issue, theoretical formulas for conduction thermal runaway under natural convection heat dissipation are proposed and validated by simulation and experiment in this paper. Results indicate that the minimum conduction thermal runaway temperature under natural convection heat dissipation is approximately 50 ℃ higher than that with nearly constant thermal resistance.