The effect of VTH hysteresis on switching characteristics of SiC MOSFETs is investigated by TCAD in this paper. A device-circuit mixed-mode simulation model is built to simulate VTH hysteresis. The result illustrates that VTH hysteresis decreases VTH and increases channel mobility, which leads to earlier turn-on and larger ID. Moreover, the higher the interface state density (Dit) is, the more obvious the transient effect. However, ID remains unchanged with VTH hysteresis and it decreases with higher Dit without considering VTH hysteresis. Therefore, the VTH hysteresis is beneficial and the findings can be useful for distributing Dit when modeling the chip process.