With the goal of improving the performance of planetary gear train transplanting mechanism, the direct connection between convexity of pitch curve and the ideal transplanting trajectory was established. A method was proposed to abstract the parameters of a planetary gear train with noncircular gears based on the convexity of non-circular gear pitch curve index. Firstly, a global reference coordinate system was established based on the transplanting trajectory;next, the planetary gear train was simplified to a two-link, two degrees of freedom, and open loop chain mechanism with two revolute joints (a 2R mechanism), and a mechanism motion solving model was established based on ideal transplanting trajectory. According to the conversion relation between transmission ratio curve and non-circular gear pitch curve, the non-circular gear pitch curve convexity judgment index was put forward. The range of the transplanting mechanism with planetary gear train central position, namely the analytic domain was established. According to the kinematics principle, the ideal transplanting trajectory was replayed by a two-link, two degrees of freedom and open loop chain mechanism. The transmission ratio of gear train was calculated, and the calculation and distribution model of transmission ratio was established. The parameters of transplanting mechanism were calculated, such as the length of links, length ratio of link, and non-circular gear pitch curve convexity judgment index. The parameter information diagram of transplanting mechanism with a given transplanting trajectory was drawn. According to the requirements of transplanting agronomy, the engineering practical solution was preferred in the information map. And the blindness of adjusting non-circular gear pitch curve was avoided. The method was used to calculate and analyze several common transplanting trajectories. The eagle-nosed transplanting trajectories were chosen to design the transplanting mechanism with planetary gear train. Simulation analysis showed that the simulation trajectory and the test trajectory were basically the same as the given ideal trajectory. The correctness of the calculation model and the feasibility of the design mechanism were verified.