Abstract: The permanent magnet AC servo drive systems generally require Hall sensors to collect motor rotor position information and three-phase winding current information. Aiming at the problem that at least 4 current or position sensors are needed in the modern motor control process, and combining the improved current reconstruction technology with the sliding mode control technology, the FOC control of the permanent magnet synchronous motor based on a single current sensor is realized. The improved current reconstruction technique is realized only by measuring the bus current of the voltage source inverter. Finally, the closed-loop control is realized by using one current sensor through algorithm optimization, which improves the system reliability and reduces the system cost.