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Reasonable planting pattern can increase soybean yield. At present, soybean cultivation models in the cold region of northeast China mainly include conventional ridge planting mode, three row planting pattern on big ridge and four row planting mode on big ridge. The compact planting pattern of big ridge three-row is becoming popularizing gradually. The big ridge three-row reduces the row spacing, increases plant spacing and plant density than the traditional planting pattern. This way of planting soybean increases crop yield by reducing row spacing between soybean plants to increase planting density and to increase the number of plants protected per unit area. The three-row soybean planting pattern means that three rows of soybean are planted evenly on the ridge table of 1.1 m big ridge, and the marginal effect of the ridge platform is fully utilized. The outermost two rows of soybean are 400 mm apart and the spacing of each row of soybean is 200 mm. According to the agronomic requirement and technology for the model of compact planting soybean with three rows on 1.1 m grand ridge, the problem of compact structure and poor passing ability on planting unit are caused by the matching planter that uses single-row planting unit devices in dislocation parallel. The pneumatic cylinder precision seed-metering device for soybean matching compact planting soybean with three rows on 1.1 m grand ridge is designed, combined the features of mechanical clearing and gravitational dropping. The structural parameters of the key components of the three-row soybean seed-metering device on ridge are determined. The diameter of the cylinder is 200 mm, the length of the cylinder is 500 mm, the axial hole of the cylinder is 3 rows and the distance is 200 mm, and the number of single row holes is 40. The sealing problem of the pneumatic cylinder seed-metering device is solved through the innovative design of the structure. In order to effectively remove multiple seeds adsorbed on the hole and keep only one seed in each hole, a scraper seed cleaning device is designed. In order to ensure that the seed can be planted freely in the seeding area, a pressure relief device for isolating the pressure difference inside and outside the hole is designed. In this study, the key structural parameters and the mechanical model of seed-filling process were determined through theoretical analysis. The experiment was employed through the method of quadratic orthogonal rotating center combination of three factors and five levels according to the GB6973-2005 national standard. In test, soybean seed Heinong 48 was selected as experimental material. Combining with extensive pre-experiment and theoretical analysis, the vacuum degree, forward speed and hole diameter were taken as main influencing factors, the seed qualified index, multiple index, missing index and variation coefficient of apiece row seeding mass were taken as response index. The results showed that: the order of the contribution rates on the effect of qualified index was vacuum degree, working speed, hole diameter, the order of the contribution rates on the effect of multiple index was vacuum degree, hole diameter, working speed, the order of the contribution rates on the effect of missing index was vacuum degree, working speed, hole diameter, the order of the contribution rates on the effect of variation coefficient of apiece row seeding mass was, working speed, vacuum degree, hole diameter. The optimal combination of parameters was as follows, the hole diameter was 4.5 mm, the vacuum degree was between 4.7 and 5.9 kPa, the working speed was lower than 9.1 km/h, and under the optimal combinations, the qualified index was not less than 95%, the multiple index was not more than 3%, the missing index was not more than 2%, and the variation coefficient of apiece row seeding mass was not more than 6.5%. The verification test was repeated 10 times on the JPS-12 seed-metering test beds, the results were indicated that the actual test results were in agreement with the optimization results. The results of the research laid a foundation for the development of pneumatic cylinder grand ridge three-row seed-metering device for soybean, and provided a reference for the research of soybean narrow-row and flat-dense planter. [ABSTRACT FROM AUTHOR]