Pepper is an important domestic economic crop that has a high economic benefit, and its large-scale mechanized planting can further reduce its production cost. However, as a crop planted in various regions in either field or greenhouse, pepper transplantation with the semi-automatic transplanter remains labour intensive and with low efficiency, and research on the automatic seedling picking and throwing device is in urgency. Hence, a double row stem clipping type automatic picking and throwing device for commercial 2ZBX-2 vegetable semi-automatic transplanter was designed. The cyclic picking and throwing assignments were realized for pepper pot seedlings through the two rows of clipping jaws that equipped on two face to face type mechanical arms, and orderly and smooth operation and the picking and throwing device was guaranteed by the PLC control system. The key components of clipping jaw were the soft materials and the spring steel sheet that fitted tightly, and accurate positioning of clipping jaw was realized with the horizontal and vertical motion mechanisms. Effect of soft material thickness, age of pepper seedling and cylinder pressure of clipping jaw on picking failure rate, delivering failure rate and throwing failure rate was analyzed by single test, and an orthogonal test was conducted, with the picking-throwing success rate as an optimal object, to determine the optimal working parameters. Under the optimal working parameter combination that soft material thickness was 10.0mm, age of pepper seedling was 51d, and cylinder pressure of clipping jaw was 0.40MPa, the test showed that the average real pickingthrowing success rate reached 94.6%, which basically met the technical requirements of vegetable transplanting operation.