In order to feed the seedling automatically and to solve problem of seedling leakage，an automatic seedling feeder which can convey the cotton seedling horizontally and longitudinally according to granville2-ZQ4 type semi automatic bare-rooted cotton seedling transplanter. In addition, a control system for detecting seedling was designed, which accelerate the feeding speed when no seeding was detected, and enable the feeder catch the seedling normally without leaking. The motion simulation analysis showed that the motion trajectory of the designed seedling feeder is “bow” shaped and the interval for sending a seedling is 1.6 s, which could achieve the expected goal and satisfy the requirement of bare-rooted cotton seedling transplanter.