Abstract: In order to solve the high-precision control problem of a permanent magnet synchronous motor (PMSM), a discrete type active disturbance rejection control (ADRC) method based on improved particle swarm optimization algorithm was proposed. On the basis of the mathematical model of PMSM, the conventional particle swarm optimization algorithm was ameliorated, the second-order tracking differentiator, the third-order extended state observer and the nonlinear state error feedback unit were designed and improved, and a new nonlinear function was designed and used to improve the control rate of the extended state observer and the nonlinear state error compensation. The improved particle swarm optimization algorithm was responsible for tuning the parameters of the state observer and the nonlinear state error compensation. The results show that compared with PI controller and the traditional ADRC, the improved ADRC based on particle swarm optimization made the PMSM have faster response speed, better tracking accuracy and stronger anti-interference ability, and significantly improve the control effect.