Threshold voltage is a widely-used thermal-sensitive electrical parameter and health condition indicator for power devices. Hence, its accurate measurement is important for the reliability assessment of power devices. This paper presents a method for quasi-online and non-invasive measurement of the threshold voltage of silicon carbide (SiC) MOSFET. The measurement circuit operates when the power device is not operating, which has the advantage of a simple circuit topology and low sampling bandwidth requirements. The operating principle and hardware design of the measurement circuit are introduced. The measurement circuit is evaluated experimentally at different current levels and junction temperatures. The experimental results show that the threshold voltage can be measured accurately and its linear relationship with the junction temperature is also verified experimentally.