This unit is more applicable for granulating the different kinds of waste plastic than the single-step machine. The finished granules have the higher smooth finish with the material of wet waste plastic. The granules have the lower ratio of the holes inside and the higher output after Three-step exhausting than the same type machine. The main engine equipped with the hydraulic screen changer can continue producing and save the manpower without shutting down the machine, breaking plastic strips and remaining leftover material.