In　recent　years,　a　plant　factory　has　gradually　become　a　new　model　of　facility　agriculture,　and　the　optimization　problem　of　low　-carbon　design　of　production　system　in　a　plant　factory　has　become　more　prominent.　In　the　design　of　the　production　system,　needs　of　high　efficiency,　high　yield,　and　low　carbon　emission　must　be　considered.　In　this　study,　the　leafy　vegetable　factory　is　taken　as　the　research　object,　and　the　carbon　footprint　calculation　model　of　products　is　established　based　on　the　life　cycle　assessment　method.　Taking　production　capacity　and　carbon　footprint　as　design　indicators,　the　logical　correlation　and　mathematical　relationship　between　them　and　production　line　design　parameters　are　analyzed　layer　by　layer　to　determine　the　key　design　parameters.　The　leafy　vegetable　production　line　is　modeled　by　plant　simulation　software,　and　multifactor　simulation　experiments　are　set　up　to　explore　the　influence　of　key　design　parameters　on　design　indexes　to　guide　the　optimal　decision　of　parameter　design　scheme.　The　new　design　scheme　increases　the　productivity　of　the　plant　factory　by　35.40%,　reduces　the　carbon　footprint　of　leafy　vegetables　by　15.54%,　and　solves　the　problem　that　leafy　vegetables　at　the　bottom　of　the　planting　frame　in　the　original　plant　factory　grow　poorly　because　of　insufficient　light.