Wood chip winnowing system

The invention provides a wood chip winnowing system which is arranged between a flaking process and a hot grinding process on a fiberboard production line and is used for screening qualified wood chips from flaking primary materials. The system comprises a material conveying belt, a flat tuyere, a first collecting channel, a second collecting channel and a third collecting channel, the material conveying belt is arranged in a downward inclined mode from the feeding port, so that materials are evenly spread and conveyed from the feeding port to an air blowing port of the flat type air nozzle at a constant speed. The flat tuyere is obliquely arranged upwards from the air source, and an air blowing opening of the flat tuyere is closely positioned below the terminal of the material conveying belt, so that materials are obliquely intersected with airflow along the airflow direction of the flat tuyere; and the first collecting channel, the second collecting channel and the third collecting channel are respectively