The loss calculation accuracy of a three-phase full-bridge inverter will be reduced if the parasitic capacitance and parasitic inductance loss of SiC MOSFET in the switching process and the conduction loss caused by changes in the duty cycle in the conduction process are ignored. To solve the problems, a physical model of SiC MOSFET considering parasitic capacitance and parasitic inductance was proposed. The parasitic capacitance and parasitic inductance were obtained by querying a data sheet and using an oscillation method. The losses of parasitic inductance and parasitic capacitance during the switching process were calculated, the average conduction loss equation under space vector pulse width modulation (SVPWM) was deduced, and the three-phase full-bridge loss was obtained. Finally, experiments were carried out on the control system of a permanent magnet synchronous motor based on SiC MOSFET. The influence of PWM frequency on the three-phase full-bridge loss was analyzed, and the accuracy of parameters for the physical model of SiC MOSFET was verified. Moreover, the loss calculation method based on the physical model of SiC MOSFET can improve the loss calculation accuracy of the inverter.