The integrated mathematical model of an interior permanent magnet synchronous machine (IPMSM) system is set up suitable for healthy state, open-circuit fault state and fault-tolerant state in this paper. An on-line open-circuit fault diagnosis method is proposed, the fault-tolerant structure is set to connect the fault phase to the middle of DC link, considering that DC link voltage is not balanced, therefore, an optimized adaptive space vector pulse width SVPWM of four-switch three-phase inverters (FSTPI) under DC-link voltage ripple condition is presented to achieve the maximum torque per ampere (MTPA) control and flux weakening control of the IPMSM system under the fault-tolerant state. Based on the abovementioned research, system simulations are implemented and simulation results are given.