In order to meet the requirements of dryland pot seeding transplanting mechanism, which need to achieve ideal “olecranon shaped” track, a continuous transmission seedling pick-up mechanism of planetary gear train with second-order general non-circular gears was proposed so as to achieve the seedlings claw periodic secondary unequal amplitude swing. The curve fitting method was utilized to build free transmission function, and a mathematical model about non-constant velocity drive of mechanisms was established, The mechanism analysis software was compiled, and the transmission ratio functions and mechanism parameters were determined to manufacture the seedlings transplanting mechanism. The high speed video test was carried out, The results showed that the seedlings test trajectory could agree well with theoretical calculations. The depth of taking seedlings was deeper than 35mm, and the scoop of pot was less than 5mm. The posture of seedlings claw met the job requirements during plunging into pot and quitting pot process.