The invention relates to the technical field of industrial equipment, and discloses a ball mill for grinding a soft magnetic core. The ball mill comprises a fixing box, a rotating cylinder, a lining,grinding steel balls, an outer gear and a key, wherein the lining is fixedly arranged on the inner wall of the rotating cylinder, the outer gear is fixedly arranged at the bottom of the rotating cylinder in a sleeving mode, the grinding steel balls are movably arranged inside the lining, a bottom support seat is fixedly arranged on the fixing box, and a large thrust bearing is fixedly arranged inside the bottom support seat. Due to the arrangement of the rotating cylinder and a partitioning device, the space inside the rotating cylinder is equally divided, the effective grinding space is further compressed, the impact efficiency between the grinding steel balls and a material is improved, the grinding effect in the area is improved, and the grinding efficiency is improved; and the rotatingcylinder and the partitioning device are rotated in different directions, so that the movement track and the movement speed of the grinding steel balls are increased, the impact times among the grinding steel balls and between the grinding steel balls and the material are increased, and the grinding effect on the material is further improved.