Abstract: The small gap between rapeseed could cause difficult heat dissipation and seed drying, and result in mildew of rapeseed. To tackle this problem in production, we designed a spin dryer on the principle of drying rapeseed with cyclone airflow. Base on the force analysis of rapeseed following the airflow movement in the drying chamber, we discovered the relations between the size of grading hole and the moisture content of rapeseed, and designed the structure of air blower and heater, then tested the demo dryer. The results showed that when inlet temperature of the dryer was 80℃, the wind speed of the dryer was 19 m/s and the diameter of the classifier was 135 mm, the water losing rate of rapeseed was 1.0833 %/min and the water content of rapeseed was 7.65% after being dried, which met the agronomy requirements for dried rapeseed.