The precleaner can separate two kinds of impurities, large and small from the raw materials at one time, and can clear light impurities after the aspiration system of the outlet of finished product connects with the air piping. Driving mechanism with compact structure . Four sides are set large opening doors,ease of maintenance. According to different materials,the inclination angle of screening drum can be optionally adjusted within a scope of 4°-8°in order for best cleaning results. The screen sieve is detachable, ease of replacing and saving costs. The outlet of inside screening drum near is equipped with oriented screw,helping to remove large impurities and meanwhile prevent the materials from outflowing along with large impurities. Mainly used for granular material cleaning in industries such as grain storage, food, chemical, mining and so on.