It uses plate hammer on the rapidly rotating rotor to generate high-speed impact to crush the materials in the crushing cavity, and casts the crushed materials along tangential direction to impact plate at the other end of the crushing cavity. The materials are crushed again, and then, they return to the plate hammer to undergo the process above repeatedly. The materials are bumping with each other when being sent between the plate hammer and the impact plate. The materials become cracked, loose and then comminuted by knocking by the plate hammer, impact with impact plate and bump between materials. The materials with grain size smaller than the gap between impact plate and plate hammer will be discharged.