Abstract: With the widespread application of power devices in aerospace, rail transit, and electric vehicles, their reliability has garnered significant attention. Accurate estimation of device junction temperature is crucial for ensuring the operational reliability of power electronic systems, and it is also the basis for realizing the life prediction and health management of SiC MOSFET devices. Focuse on SiC MOSFETs, the relationship between the drain-source voltage fall time(t_fv) during the turn-on process and the junction temperature is investigated. Based on this relationship, a junction temperature measurement method utilizing the voltage fall time is proposed. A high-frequency signal-based voltage fall time detection circuit and a junction temperature detection system with switchable drive resistance are designed. Experimental results demonstrate that under high drive resistance conditions, the voltage fall time of SiC MOSFETs exhibits high-temperature sensitivity and good linearity, making it suitable as a temperature sensitive electrical parameter for measuring junction temperature. The designed detection circuit accurately extracts the voltage fall time, while the constructed junction temperature detection system enables online temperature monitoring.