The causes of the torque ripples of a brushless DC motor (BLDCM) were analyzed and an active disturbance rejection controller (ADRC) was designed to control the torque ripple reduction of the brushless DC motor.A state observer of the controller was adopted to detect the phase current ripple of the system.And the offset value of the detected current ripple deviation was compensated by the non-linear state feedback control rate of the controller to achieve the suppression of current ripple,which forms a BLDCM double closed-loop control system to achieve the suppression of torque ripple.The simulation results show the value of torque ripple of the brushless DC motor designed is 9%.The ADRC eliminates the overshoot generated by the system and the feedback can be fully and smoothly tracked.In short,the designed ADRC can better suppress the pulsation of the torque by compensating the offset of the current ripple error.