Feed areas of cyclonic classifier was divided according to air velocity distribution characteristics. The effects of three representative feed positions on particle trajectory and classifying accuracy was investigated and force on 1 μm and 10 μm particles in different areas was analyzed by unsteady discrete particle model and classification experiments. Near-wall feeding mingled fine particle into coarse powder and impaired classification accuracy. Near-center feeding exerted strong centrifuge force on coarse particles and high axial shear force on fine particles by high flow field intensity which reduced particle residence time in classification zone and achieved rapid classification with improved classification efficiency. Center feeding extended classification move distance of coarse particles and increased possibility of coarse particles going into fine fraction

which simulation showed that 11.7% of 15 μm coarse particle by mass was mixed with fine powder. Experimental results showed that near-center feeding at inlet air velocity in a range of 10 m·s-1 to 22 m·s-1 minimized overlap between distribution curves of coarse and fine particles and increased average ratio of classified particle diameter by 25.3%. Those results could provide guidance to design feed position of air cyclonic classifiers.