The materials are uniformly sent to the first chamber of the dry ball mill by the feeding device through the feeding hollow shaft. The first chamber of the dry ball mill contains stepped lining board or corrugated lining board, and steel balls of different specifications. The centrifugal force generated by the cylinder rotation will bring the steel balls to a certain height and then drop down, which will have a pounding and grinding effect on the materials. After the rough grinding is finished in the first chamber of the dry ball mill, the materials will enter into the second chamber through the single-wall partition, which is lined with the flat lining board and steel balls to further grind the materials. The powder material is discharged through discharge grates, then the grinding operation is completed.