In view of the difficulty in separation and cleaning caused by the great difference of agronomic morphology and complex physical characteristics of the components of the exfoliates during the mechanized harvesting of Chinese cabbage seeds, a separation and cleaning device composed of an internal flow cylindrical sieve (with a inner spiral auger) and a crossflow suction fan was designed. The structure and working principle of the device were described, and the structure and working parameters of its key components were determined by theoretical analysis.The rotational speed of the cylinder sieve, the inner spiral auger and the crossflow fan were selected as the test factors, the hybrid rate and the loss rate were taken as the performance indexes, the orthogonal test was carried out, and the optimum working parameter combination of the device was obtained by using the comprehensive scoring method and the test was verified.The results showed that the main and second order of the test factors that affected the cleaning performance of the device were speed of the crossflow fan, speed of the cylindrical screen and speed of the auger, and the optimal parameter combination of the separation and cleaning device was speed of the crossflow fan of 70r/min, speed of the auger of 200r/min and speed of the crossflow fan of 700r/min.The performance verification test was carried out under the parameter combination, and the results showed that the impurity content and loss rate of Chinese cabbage seeds were 2.75% and 0.62% respectively, which met the requirements of relevant industry standards. 