Magnetic polishing is a processing method that uses a magnetic force to restrain the abrasive and precisely polish the workpiece. This study explores the effect of motor control mode on drum-type magnetic polishing. The servo motor is driven by the coupling through the coupling to perform the grinding experiment, and the servo motor rotation mode is changed. Disturbance occurs when the abrasive is ground in the drum in a forward and reverse running mode. Therefore, The surface is ground more smoothly and evenly. This paper studies the effects of various parameters on surface roughness and surface removal. The results show that the average speed of the trapezoidal wave is higher than that of the Sin waveform. Therefore, regardless of the average roughness or the amount of removal, the motor mode is better when the trapezoidal wave is reversed. The magnetically conductive test piece will have an uneven grinding effect due to the adsorption of the magnetically conductive abrasive on the test piece.