Extraction components of threshing unit for rape combine harvester are complicated, including rapeseed, stems, pod shells and light debris. To study the aerodynamic characteristics of rape extraction components, test suspension velocities of these components were conducted in type PS—20 measuring test-bed respectively. The results showed that the linear relationship between suspension velocity of rapeseed and particle size was exposed. The quadratic polynomial relationship between the suspension velocity of stem and diameter was exposed. The stem length (<100mm) revealed there was no significant effect on the suspension velocity. Suspension velocities of rapeseed and stems were observed to be closer (7~10m/s), higher than suspension velocities of pod shells and light debris (1~3m/s). Meanwhile, suspension velocities of rapeseed and pod shells both was exposed a linear increase relationship with the moisture content, while suspension velocities of stems and light debris both was exposed an exponential increase relationship with the moisture content. It’s concluded that the difference of their suspension velocities could be applied for cleaning the extraction components. The suspension velocities of light debris and pod shells were small in extraction components. The air flow cleaning method was suggested to separated them and the airflow velocity was 4~6m/s.