Four-shaft series shredders are of multifunction and versatility. With standardized and modular design, shredder of this series has an advantage of good interchangeability between spare parts. The auxiliary knife is refined by die forging, while the main knife, made of special alloy steel by a special process, is of good wearability and high intensity. The shredder is driven by intermediate gear transmission, forming differential relationship. Shredders of this series are applicable to shred plastic barrels, plastic frames, woven bags, circuit board and paper box etc., and have advantages of controllable discharging size, high-efficiency, low rotate speed and low noise.