Belt type negative pressure winnowing machine

The utility model discloses a belt type negative pressure winnowing machine which comprises a machine frame, an air bellow assembly and a conveying belt, the conveying belt is of a closed runway-shaped structure, through holes are evenly distributed in the surface of the conveying belt, the conveying belt is arranged on the outer side of the air bellow assembly in a sleeved mode, and the conveyingbelt is connected between supporting plates of the machine frame. One end of the supporting plate is connected to the inner side of the conveying belt through a driven roller, the other end of the supporting plate is connected to the inner side of the conveying belt through a driving roller, a positive pressure air box and a negative pressure air box are arranged at the two ends of the air box assembly respectively, and the positive pressure air box is arranged on one side of the driving roller. The negative pressure air bellow is arranged on one side of the driven roller, the lower portion of the negative pressure a