The invention relates to a planetary gear type magnetic composite fluid polishing device. According to the technical scheme, a bearing seat is fixedly connected to the lower end of a case, the lower end of the bearing seat is rotationally connected with a shell through a limiting plate, a motor is fixedly connected in the case through a mounting plate, a main shaft of the motor is fixedly connected with a rotating shaft through a coupler, the upper part of the rotating shaft is installed in the bearing seat through a bearing, the lower part of the rotating shaft is connected with a bottom plate of the bearing seat through a U-shaped bearing, the U-shaped bearing is fixedly connected with a needle rod positioned in the shell, the upper part of the needle rod is fixedly connected with a mainplanet gear, the main planet gear is meshed with an auxiliary planet gear, the auxiliary planet gear is meshed with an inner gear on the upper part of the shell, moreover, the auxiliary planet gear is rotationally connected with the needle rod through a connecting shaft, a plurality of magnet rings are fixedly connected to the lower part of the needle rod, moreover, the magnet rings are arrangedin the shell. The motor drives the needle rod to drive the main planet gear and the connecting shaft to rotate, then the auxiliary planet gear is enabled to rotate around the main planet gear, the auxiliary planet gear enables the inner gear and the main planet gear to rotate reversely, and then the rotating direction of the shell and the rotating direction of each magnet ring are opposite.