Abstract: Abstract: A sunflower seed is one of the most important cash crops in oil, food, and feeding. The area of edible sunflower cultivation has steadily increased in China in recent years. It is an urgent need for mechanized and combined harvesting. However, the conventional machinery of edible sunflower harvesting cannot fully meet the large-scale production, due to the low seed selection and adaptability in fields. Among them, the fan-shaker structure is adopted for the current cleaning device in the 4ZK-6 type combined harvester of edible sunflower. It is a high demand to develop a new device suitable for steep slope, where edible sunflower is widely grown. In this study, a cylinder sieve device was designed for the combined harvesting operation under the complex terrain, according to the threshing mixture characteristics of edible sunflower. The size of the sieve aperture was set as 16 mm using the average three-axis diameter and particle size of the edible sunflower seed, broken petiole, and broken sunflower plate in the threshing mixture. The range of the inclination angle was obtained to clarify the effect of the inclination angle of the sieve on the performance of the seed sieve using the size of the stripped material particle. The kinematics analysis of edible sunflower seed was combined with the actual production needs. The structure size of built-in flow-aided spiral blades was determined as follows: the outer and inner diameters were 670, and 500 mm, respectively, while the pitch was 400 mm. A dynamic analysis was performed on the sliding and throwing out of edible sunflower seed on the cylinder sieve surface. The range of velocity was then determined in the cylinder sieve. Software EDEM was selected to determine the axial motion velocity of materials in the cylindrical sieve with the sifting time, and the sifting characteristics of edible sunflower seeds with the size of the selected sifting hole. The single-factor test was carried out to clarify the influence of the inclination angle, the rotational velocity of the cylinder sieve, and the feeding amount on the seed clean rate and loss rate. The threshing mixture of "Sunflower 363" was selected as the research object in Hebei Province and Inner Mongolia Autonomous Regions, China. The optimal intervals of working parameters were determined for each factor. The orthogonal test was carried out using cleaning rate and loss rate as evaluation indexes under SPSS software. Variance analysis showed that the rotational speed and feeding amount of the cylinder sieve posed a significant effect on the clean ratio and loss ratio, whereas, the inclination angle of cylinder sieve installation had a significant effect on the clean ratio, but some effect on the loss ratio. The comprehensive scoring demonstrated that the order of the primary and secondary factors on the cylinder sieve selection was ranked as inclination, the speed of the cylinder sieve, and feeding amount. The optimal working parameters of the cleaning device were achieved in the feeding amount of 0.6 kg/s, the sieve installation inclination of 3°, and the speed of 25 r/min. The bench test indicated that the clean and loss ratios were 98.92% and 1.97%, respectively under the optimal combination. A field test was carried out in Wuchuan County, Inner Mongolia Autonomous Region, China. The test subject was chosen as the "sunflower 363" with the 800 mm+400 mm wide and narrow planting mode, where the plant spacing was 500 mm. Three 20-metre slopes were selected in the steeply sloping areas, in order to verify the performance and adaptability of the cylindrical sieve cleaning device in complex working conditions. Specifically, the clean and loss rates were 96.53%, and 2.08%, respectively, indicating the stable operating performance of the cylinder sieve device. The clean rate of the whole machine was 3.32 percentage points higher than the original fan-shaker cleaning structure, while the loss rate was reduced by 4.11 percentage points. The cylinder sieve device can be expected to effectively improve the performance of edible sunflower combine harvester in complex terrain. This finding can provide the theoretical reference for the structural optimization of edible sunflower harvesting equipment.