In order to realize the automatic transplanting of potted vegetable seedlings, a non-circular gear transmission mechanism with large coincidence degree was proposed, which can reduce the transmission error caused by the tooth side clearance between gears and improve the motion accuracy. Then, according to the agronomic requirements of potted vegetable seedlings, the seedling taking track of close planting transplanting and an eight row synchronous seedling taking mechanism of non-circular gear planetary gear train based on the transmission mechanism were designed. The reverse design of seedling picking mechanism was carried out, its kinematics was analyzed, and the reverse design software of dense planting transplanting seedling picking mechanism was independently developed. In order to reduce the transmission error, the primary gear transmission of the planetary gear train seedling taking mechanism adopted non-circular gear transmission with large coincidence degree, and the secondary gear transmission adopted helical gear transmission, and the coincidence degree of each gear transmission was close to 2. Based on the virtual prototype technology and high-speed camera technology, the trajectory test of the seedling taking mechanism was carried out, and the test and simulation seedling taking trajectory were obtained. Compared with the theoretical calculation trajectory, the three trajectories were basically consistent, which verified the correctness and feasibility of the design of seedling taking mechanism for close planting transplanting. The seedling taking test of the dense planting transplanting seedling taking mechanism was carried out. The success rate of the seedling taking mechanism was about 95%. The performance of the prototype mechanism was tested.