Prefabricated　steel　structure　with　earthquake-resilience　has　become　one　of　the　hot　topics　in　the　field　of　seismic　engineering.　Based　on　the　idea　of　damage　control,　this　paper　proposes　a　new　type　of　earthquake-resilient　prefabricated　beam-column　steel　joint　(PBCSJ)　with　double　flange　cover　plates　(FCPs),　which　is　formed　by　a　circle　tubular　steel　column　with　a　cantilever　beam,　an　independent　beam　and　a　set　of　connecting　devices　in　between.　After　the　comprehensive　analysis　of　the　mechanical　behaviour　of　PBCSJ,　the　formulas　are　derived　from　three　aspects:　the　thickness　of　FCPs,　the　number　of　flange　connection　bolts　and　the　middle　bolts　interval.　Then　the　design　theory　of　earthquake-resilient　PBCSJ　with　double　FCPs　is　established　in　this　paper,　and　its　rationality　and　applicability　are　verified　by　11　groups　of　57　numerical　examples.　The　study　shows　that　the　design　theory　can　be　used　to　accurately　calculate　the　yield　load　of　PBCSJ.　The　sliding　moment　of　flange　connection　bolts　and　the　ultimate　load　of　PBCSJ　also　can　be　controlled　effectively.　The　joints　designed　according　to　this　theory　have　superior　bearing　capacity　and　ductility,　which　ensures　that　the　beams　and　columns　are　kept　in　elastic　stage　and　provides　preconditions　for　post-earthquake　repair　of　PBCSJ.