The　jacking　mechanism　of　ZGM-7　automatic　tray-seedling　grafting　machine　developed　by　our　research　group　has　failure　problems　in　the　process　of　jacking　seedling　by　needle.　For　solving　those　failure　problems,　the　software　EDEM　(enhanced　discrete/distinct　element　method)　is　used　in　the　research　of　the　process　of　jacking　seedling　by　needle　in　this　paper.　The　Edinburgh　elastic-plastic　cohesion　model　(ECM)　is　chosen　as　particle　contact　model　and　a　variety　of　complex　particle　models　with　various　material　properties　are　established　to　simulate　the　realistic　seedling　substrate　in　the　software　EDEM.　Furthermore,　the　relationship　between　the　mechanism　and　the　seedling　substrate　is　studied　in　simulation.　It　takes　the　maximum　jacking　height　of　the　bottom　of　seedling　substrate　as　index　parameter　and　analyzes　the　principles　how　the　different　factors,　including　needle　diameter,　needle　length　and　jacking　speed,　influence　the　process　of　jacking　seedling　by　needle.　The　simulation　and　experimental　tests　are　designed　and　performed　by　response　surface　methodology.　The　actual　experimental　result　is　consistent　with　the　simulation　result.　The　both　results　show　that　needle　diameter　and　jacking　speed　have　a　significant　influence　on　the　maximum　jacking　height　of　the　bottom　of　seedling　substrate,　and　the　interaction　between　needle　diameter　and　jacking　speed　is　significant.　The　maximum　jacking　height　of　the　bottom　of　seedling　substrate　increases　monotonically　and　then　slowly　decreases　monotonically　with　the　increasing　of　needle　diameter　in　the　test　level.　The　maximum　jacking　height　of　the　bottom　of　seedling　substrate　increases　monotonically　with　the　increasing　of　jacking　speed　in　the　test　level.　The　maximum　jacking　height　of　the　bottom　of　seedling　substrate　increases　with　the　increasing　of　jacking　speed,　when　the　needle　diameter　is　large.　The　maximum　jacking　height　of　the　bottom　of　seedling　substrate　decreases　with　the　increasing　of　the　needle　diameter,　when　the　jacking　speed　is　small.　The　maximum　jacking　height　of　the　bottom　of　seedling　substrate　gradually　increases　and　then　decreases　with　the　increasing　of　the　diameter　of　steel　needle,　when　the　jacking　speed　is　large.　The　error　between　simulation　and　experiment　result　is　only　0.7%-7.2%.　Among　those　errors,　larger　errors　only　exist　in　phenomenon　of　dropping　and　crooking　seedling　substrate.　The　realistic　seedling　substrate　has　a　root　system,　which　prevents　the　insertion　of　needle.　Thus,　the　seedling　substrate　is　easier　to　be　dropped　and　crooked　early.　However,　the　error　when　vertically　jacking　seedling　substrate　is　less　than　2.1%　in　simulation　and　experiment.　The　successful　maximum　jacking　height　of　the　bottom　of　seedling　substrate　is　144　mm,　which　is　proposed　as　the　optimization　target.　The　software　Design-Expert　is　used　to　optimize　the　simulation　results　within　test　level.　The　optimal　parameters　of　the　simulation　result　are　needle　diameter　of　2.28　mm,　needle　length　of　12.28　mm　and　jacking　speed　of　0.09　mm/s.　The　simulation　optimization　parameters　are　applied　to　the　actual　mechanism.　It＇s　found　that　the　effect　of　simulation　optimization　is　significant　and　the　success　rate　of　jacking　seedlings　is　95.3%.　This　study　greatly　improves　the　operation　effect　of　jacking　mechanism　of　ZGM-7　automatic　plug-seedling　grafting　machine,　and　it　provides　reference　for　the　similar　problems　like　jacking　up　the　discrete　matrix　by　needle.　Meantime,　the　reliability　of　simulation　results　has　been　proved　in　this　paper.　So,　the　experimental　results　can　be　replaced　by　simulation　results,　which　will　reduce　actual　test　workload　significantly　and　shorten　the　equipment　development　cycle　obviously.　The　method　in　this　paper　achieves　a　good　simulation　effect,　which　can　be　applied　to　other　similar　complicated　environments.　©　2017,　Editorial　Department　of　the　Transactions　of　the　Chinese　Society　of　Agricultural　Engineering.　All　right　reserved.