A rotary transplanting mechanism with planetary elliptic gears used to transplant seedlings for automatic vegetable transplanter was described. Work principle and structural features of the mechanism were analyzed. The kinematics model was established. Based on Visual Basic 6.0, the software of aided analysis and parameters optimization for rotary transplanting mechanism were developed. Kinematics property was analyzed and simulated. Though conversations in human-computer, structural parameters of the transplanting mechanism were optimized and meet the demands of transplanting seedlings. Finally, 3-D mechanism model and simulation analysis were carried out, and the results of simulation accorded with theoretical analysis.