Abstract: In view of the exiting installation defects and apparent chaos under certain parameters of permanent magnet synchronous motor speed control systems, a sliding mode control chaos suppression method is proposed based on speed sensorless. A nonsingular fast-terminal sliding-mode control method is designed to restrain chaotic phenomenon under the basic framework of a speed sensorless vector control system fora permanent-magnet synchronous motor (PMSM). First, a chaos model of PMSM is presented and the existence of chaotic phenomena verified through simulation. The speed sensorless vector control system of the PMSM is based on an extended state observer (ESO) speed estimation. Then, based on this, a nonsingular fast-terminal sliding-mode controller, that eliminates chaotic movement when some parameters are changed, is proposed. The simulation results demonstrate that this effective method can guarantee the stability and reliability of motor operation.