e=3mm, R=19mm,α0=-40°,φ0=36°, S=155mm, H=180mm。A new type of rotary transplanting mechanism with planetary gears, which is used to transplant seedlings for high-performance rice transplanter, was introduced Work principle and structural feature of the mechanism were analyzed, and its kinematic models were established. Parameters optimization software based on Visual Basic 6.0 was programmed. Kinematic property was analyzed and simulated, based on the optimization method of human-computer conversation, then structural parameters of the transplanting mechanism were obtained, which could meet the demands of transplanting seedlings, such as, e=3mm,R=19mm,α0=-40°,φ0=36°, S=155mm, H=180mm.