An automatic delivery mechanism of potted-seedling for vegetable transplanter based on PLC was designed. The automatic mechanism of taking potted-seedling from pot with non-damaging was designed. The ejector pin driven by high speed servo electric cylinder was used. The potted-seeding was taken from the pot with precise, high speed and non-damaging. The potted-seedling was located and transplanted precisely by the stepping motor which was controlled by the software system of PLC. The casting potted-seedling mechanism synchronously, consisted of the timing belt and gear, was designed, which realized the synchronous movement between the casting potted-seedling unit and the duckbilled-type planting shoe. The problem of non-uniform rotation velocity of duckbilled-type planting shoe driven by ground wheel was solved. The seedling accuracy was increased. At last, the device was designed, which verified the correctness of automatic delivery mechanism.