Power semiconductor devices are frequently used in the electronic and power industries. As the third-generation broadband gap power semiconductor devices, silicon carbide devices have attracted extensive attention. This paper introduces the internal and external structure of SiC MOSFET in detail and analyzes the basic working principle of SiC MOSFET and the electrical characteristics of each stage in the conductive process. By analyzing the theoretical calculation method of threshold voltage under body effect and the relationship diagram drawn by specific experimental test results, it is proved that the increase of body effect will lead to the decrease of the threshold voltage. Two main reasons for BTI characteristics are explained: the energy band shift of the SiC/SiO2 interface is small, and there are many charge traps at SiC/SiO2 interface. Finally, the theoretical calculation method of threshold voltage and the influence principle of threshold voltage drift caused by SiC/SiO2 interface charge: interface trap Qit, oxide trap Qot, movable ion Qm and fixed charge Qf are analyzed. The research on the basic principle and important characteristics of SiC MOSFET in this paper have important reference significance for improving the reliability of SiC MOSFET devices.