Abstract: In order to reduce the breakage of cut stem after pneumatic separation, the effects of conveying air velocity after pneumatic separation and moisture content of cut stem after drying on the structure of cut stem were tested.The results showed that 1)the higher the air velocity was, the higher the breakage would be;2)the higher the moisture content was, the lower the breakage would be;and 3)in practical production, the suitable moisture content of cut stem was about 13.5% and the conveying air velocity should be as low as possible on the premise of ensuring the separating effect of pneumatic separating chamber.