Four-shaft shredder is equipped with four sets of shearing cutter rollers. Four sets of cutter rollers adopt different cutter structures to cooperate with each other. After the material enters the shredding chamber, the material is torn into small pieces by the cutters tearing and shearing action on the four sets of cutter rollers. The discharging size is controlled by screen mesh. After shredding, the material smaller than the screen mesh will fall out, the bigger material will keep larger keep shredding in the shredding chamber until it can pass the screen mesh.