To improve the control performance of a three-phase permanent magnet synchronous motor with a single current sensor, a current reconstruction method based on full-order sliding mode observer and a quasi-proportional resonant regulator is proposed. First, the mathematical model of the full-order sliding mode observer is established in the two-phase stationary coordinate frame with the current and extended back electromotive force as the observed quantities. Then the unknown phase current error is reconstructed using a quasi-proportional resonant (quasi-PR) regulator to obtain the current error information required by the full-order sliding mode observer. Finally, the current information estimated by the observer is used to realize high-performance closed-loop vector control, and the parameter design methods of the observer and quasi-PR regulator are also provided. Compared with the traditional control method using a low-pass filter and a PI regulator, the proposed method is simple to implement and avoids the problems of phase lag and amplitude attenuation caused by the low-pass filter. The ‘hardware-in-the-loop’ real-time simulation results show that the new method reduces the dq-axis current harmonics by 10%~20% under a variety of working conditions, and has higher torque control accuracy and better dynamic performance. This work is supported by the General Program of National Natural Science Foundation of China (No. 52177202).