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Considering the problems that the existing drill or large row spacing hole-drop planter could not meet the agronomy requirements of American ginseng for narrow-row-dense-planting precision planting, and the mechanized planting of American ginseng lacked suitable planting machinery, a narrow-row-dense-planting precision planter for American ginseng was designed, which adopted multi-row parallel pneumatic needle seed metering device and planet-wheel dibbling seed guiding device. The structure principle of the planter and seed metering device was expounded and the transmission scheme of the whole machine was designed. The planet-wheel dibbling full-constrained seed guiding device was designed emphatically. The structural parameters of planetary gear systems were determined through mechanism analysis. The theoretical analysis and high-speed photography experiment of seed unloading process were carried out to determine the horizontal displacement and influencing factors of seed unloading trajectory, and determine the opening size of inserting apparatus of seed guiding device and the appropriate pressure of seed unloading. The theory and simulation analysis of seed guiding trajectory were carried out to determine the motion law of inserting apparatus and the low-position zero-speed dropping condition, and determine the profile of dropping control cam of seed guiding device. The results of field validation experiment showed that when the negative pressure of seed suction was -4.5kPa, the positive pressure of seed unloading was 3.0kPa and the working speed was 0.54km/h, the qualified rate of seed per hole was 86.2%, the multiple rate was 4.4%, the seed-missing rate was 9.4%, the qualified rate of seed depth was 92.8%, and the qualified rate of hole distance was 93.9%, which met the agronomy requirements of American ginseng planting.