Abstract: Abstract: Combined harvesting and segment harvesting were typical ways to complete rapeseed harvesting. Combined harvesting could finish all the operations in one time and had relatively high efficiency. Cleaning system was one of the key parts of rapeseed combined harvester and cleaning loss played an important role in the total loss of the mechanical operation. Considering the importance of reducing cleaning loss, further study on the adaptability of cleaning system to mechanical physical and aerodynamic property of rapeseed was necessary. Compared with the cleaning system working with fan and vibrating screen, cyclone separating cleaning system adopted airflow to make the seeds clean and had many advantages like simple structure. Unfortunately, the most of the cyclone separating cleaning systems were used for rice and wheat combined harvesters while the majority of traditional rapeseed combined harvesters used the fan and vibrating screen as the cleaning device which made the overall structure complex and large. To solve those problems, a kind of cyclone separating cleaning system for rapeseed combined harvester was designed in this paper. Main working components of cyclone separating cleaning system included cyclone separator, forced feeding conveyor, pipe and fan. The operating objects of cyclone separating cleaning system were rapeseed extractions, of which the main constituents were rapeseeds, pod and short stem. The structure and operation parameters of cyclone cylinder and forced feeding conveyor were analyzed. Single factor experiment and rotation regression design were carried out to study the effects of the air velocity, the air flow of the cyclone cylinder miscellany export and the linear velocity of the forced conveyor belt on clean ratio and loss ratio. The regression equation of the relationship between the air velocity of the cyclone cylinder miscellany export, and the clean ratio and the loss ratio was obtained, as well as the linear velocity of the forced conveyor belt. The results showed that the cleaning performance of the cyclone separating cleaning system was better when the air velocity of the cyclone cylinder miscellany export was 12-16 m/s, the air flow was 0.375-0.501 m3/s and the linear velocity of forced conveyor belt was 1.57-1.884 m/s (the initiative roller speed of the forced conveyor belt was 500-600 r/min). The optimum operation condition was: the air velocity of the cyclone cylinder miscellany export was 15.3 m/s, the air volume was 0.479 m3/s and the linear velocity of forced conveyor belt was 1.57 m/s (the initiative roller speed of the forced conveyor belt was 500 r/min). Under this condition, the clean ratio was 96.98% by calculation. The results could provide the support for the structure optimization of the cyclone separating cleaning system and the improvement of the overall structure for rapeseed combined harvester. What was more, the field experiment of rapeseed combined harvester was conducted in Huazhong Agriculture University. It turned out that the cyclone separating cleaning system worked well and the clean ratio was 90.21% while the loss ratio was 6.54%. In addition, though the cyclone separating cleaning system could obviously simplify the overall structure of rapeseed combined harvester and meet the production requirements, the operation performance of the cyclone separating cleaning system should be adjusted according to different feeding rates and rapeseed maturity degrees when the rapeseed combined harvester worked in field.