In order to solve the technical difficulties of lateral displacement and lateral deflection angle in the process of mechanically seedling picking process in wide and narrow rows of regenerated rice using existing space planetary gear transplanting mechanisms, a spatial trajectory unequal velocity planetary gear train mechanism was proposed with local planar trajectory characteristics, and a comprehensive research on the wide and narrow row transplanting mechanism was carried out based on the constraints of the position of rice gate and mechanism’s rotation center. A spatial gear train mechanism motion model based on key pose points (take seedling starting point, take seedling end point, push seedling point) was constructed, and the mechanism rod length parameters and spatial interleaved axis parameters was solved by using key pose points. The transmission ratio distribution of the mechanism was realized by optimizing the relative angular displacement parameters of the two rods. The incomplete non-circular gear pair was introduced into the space planetary gear system mechanism, and the intermittent mechanism was used to restrain the planetary axis to realize the plane trajectory segment with zero lateral offset and zero lateral angle during process of taking seedlings. Through simulation analysis and prototype test of the mechanism, the actual operation performance of the mechanism was consistent with the theoretical design, and the operation performance parameters of the mechanism were verified as follows: the transplanting mechanism had zero lateral offset during the process of picking seedlings, and zero lateral offset angle during the process of picking seedlings, the total lateral offset of pushing seedlings was 50.24mm, the picking angle was 5.18°, the pushing angle was 71.56°, the lateral angle of pushing seedlings was 16.26°, the width of the transplanting hole was 22.43mm, and the trajectory height was 289.76mm, which met the expected design requirements. Finally, the field experiment verified that the rice transplanting mechanism could achieve wide row (40cm) and narrow row (20cm) spacing plant under the equal distance taking position and the established rotation center of the mechanism, which met the requirements of wide row and narrow row planting.