The threshing cylinder is a key part of rape combine. But at present, the part’s design is mainly based on the prototype of rice threshing cylinder so there are many problems such as high loss rate and impurity percentage, poor adaptability and so on. On the self-designed test equipment of the threshing separation performance, the experiments of the threshing separation performance were conducted for rape, and the correlations among the structural and motion parameters of the threshing separation devices and the threshing separation performances were also analyzed. The experimental results showed that on the same condition, the short rasp bar cylinder had lower loss rate and lower power consumption, and there were little shore stalk and some other lighter matters in rape seed-tailings mixture to the short rasp bar cylinder.