The control quality of servo system requires not only stability, speed, and accuracy, but also strong anti-jamming ability. The permanent magnet synchronous motor (PMSM) is a multivariable and strongly coupled time-varying nonlinear system. It will be subject to different degrees of external interference. According to the advantages and limitations of fractional-order PID (FOPID) controller and active disturbance rejection control (ADRC), the fractional-order calculus concept is integrated into ADRC. In this paper, a control strategy of position servo system based on fractional-order extended state observer (FOESO) is proposed. The FOESO and fractional-order control law are designed to form a fractional-order active disturbance rejection control (FOADRC). The FOADRC controller is applied to the position loop control of the servo system. Through the experiment and performance analysis, it is proved that the FOESO can well observe the internal and external disturbances of the system, and the FOADRC has a good control effect in the position servo system. INDEX TERMS Permanent magnet synchronous motor (PMSM), fractional-order extended state observer (FOESO), fractional-order active disturbance rejection control (FOADRC), fractional-order calculus, position servo system.