A nonlinear model of faulttolerant switched reluctance starter/generator system is proposed in this paper. Based on the mathematical model of switched reluctance motor, including circuit equation and mechanical equation, an open model is built with modularization idea. The feasibility of the model is analyzed:① when the rated voltage is 380V under condition of electromotive state, the output torque can meet the needs of constant torque starting; ② under condition of electric power state, driven by the prime mover with 2 000 r/min, the noload rapid voltage building can be realized, and the voltage can be quickly stabilized at near 270 V and regulated. In view of the high opencircuit fault rate of power devices, a faulttolerant power converter is designed based on the idea of hardware redundancy. In order to verify the faulttolerant performance in the system, the simulation results show that:① the faulttolerant system at the electric state not only eliminates the deadtime of the torque, but also improves the average torque and reduces the torque ripple; ② the output voltage restores to about 270 V within 0.2 s, and the phase current also drops to the normal operating range, the faulttolerant performance is good.