Aiming at the difficulty of designing longitudinal seedling feeding mechanism of pot seedling transplanter by traditional method and the lack of efficient longitudinal seedling feeding mechanism of potted seedling transplanter for upland field, a longitudinal seedling feeding mechanism of ratchetconnecting rod pot seedling transplanter was designed. According to the characteristics of the mechanism and the requirement of longitudinal feedingseedling for upland field, the kinematics model and mathematical optimization objective were established, and the software for optimum design of longitudinal seedling feeding mechanism was developed to obtain the structural parameters that met the design requirements. According to the software optimization, the horizontal value range of each factor was obtained, the threedimensional model of the mechanism was established and the physical prototype was manufactured. The optimum design of ratchet structure was carried out and the quadratic orthogonal rotation center combination test method was used to optimize the parameters with the success rate of seedling delivery as the test index, which taking the height of ratchet driving surface, the height of ratchet positioning surface and the speed of seedling harvesting as test factors. The results showed that expected success rate of seedling delivery was 9985%, when x1=2.32mm, x2=3.5mm and x3=100r/min. To verify the test, setting up x1=2.3mm,x2=3.5mm and x3=100r/min, the success rate of seedling delivery was 99.17%, which met the design requirements. 