Abstract: In the vector control system of a permanent magnet synchronous machine, current sensors are very important for system stability and safety. To realize the fault diagnosis and fault-tolerant control when faults occur in current sensors, a simple algorithmic/logical diagnosis mechanism was designed based on αβ phase currents, and then fault judgment factors were constructed. For the case where only one current sensor fails, the current was reconstructed according to Kirchhoff's law, while for two or more sensors failure, an adaptive backstepping observer was designed based on Lyapunov's stability theorem to estimate the current and ensure the stable operation of system. Simulations and experiments were carried out under low and high speeds. The results show that this fault-tolerant control strategy can diagnose faults quickly and reconstruct the current stably, which verifies the effectiveness and reliability of the proposed method.