Aiming at the problem that the system model and parameters change when the demagnetization fault occurs in the interior permanent magnet synchronous motor, and the control performance of the controller declines seriously, a demagnetization fault model predictive MTPA fault-tolerant control strategy based on the improved STO was proposed.Considering the demagnetization fault of the motor, the change of model parameters was analyzed, the fault model was rebuilt, and the MTPA curve considering the fault state was solved. Then, aiming at the sensitivity of model predictive control to parameter changes, an improved STO observer was constructed to identify the permanent magnet flux on-line. Finally, a current model predictive controller was designed to fault-tolerant control IPMSM with demagnetization fault. Through experimental comparison, the constructed observer has better observation performance for permanent magnet flux linkage in the case of demagnetization fault, and the fault-tolerant control strategy is also better.