The pulverizing function of the hammer miller is carried out in pulverizing chambers of various steps. After being charged into the hopper, the materials enter into the working chamber under the control of plug-in plate. Under the action of centrifugal force of high-speed rotation of the movable pulverizing disc, the materials enter into first-step to fourth-step pulverizing chambers which composed of movable and fixed pulverizing discs, and under the combined action of impingement, shear and friction of pulverizing knifes and mutual impingement between materials, the materials are pulverized into powder and then discharged through sieve mesh. The fineness of powder can be controlled by changing different dia./mesh size of sieves.