The main component is a cylinder with diameter and length at a reasonable proportion. Driven by the transmission device, the cylinder rotates with the materials fed from the cylinder inlet and crushed by the falling impacts and autogenous grinding of the steel balls and ores in the cylinder. Due to the continuously feeding materials, the pressure pushes materials to the outlet and the grinded materials are discharged from the cylinder outlet. Qualified materials flow from the cylinder outlet. In wet grinding, the materials are taken out by the water flow. There are backpitch impellers in the hollow shaft, which can make the balls and coarse ores in the overflow return to the mill. With simple structure, higher operation rate, and rolling bearing, the energy conservation is significant.