The turbine grader, as a forced centrifugal grader with secondary rotator is composed of grading rotator, guide vane rectifier, and screw feeder. The materials are fed through the upper cartridge, and the grains will be sieved and well distributed by the incoming air, which brings the grain to the grading zone. The centrifugal force produced by the fast rotation of grading rotator together it the centripetal force by the pneumatic adhesion act on the grading grains. When the centrifugal force on the grain is greater than the centripetal force, the coarser grains above the grading range will be swirled down along the container wall. The secondary air will be rectified to uniform cyclone through the guide vane, and separate the thinner grains from the coarser ones. The separated coarser grains will be blown out from the discharge port. The thinner gains below the collector, whereas the purified air will be vented outside from the draft. Features