The　mainshock　(MS)　is　often　accompanied　by　a　number　of　aftershocks　(AS).　The　existence　of　AS　may　cause　the　seismic　demand　to　be　greater　than　the　MS.　In　order　to　better　evaluate　the　impact　of　AS,　this　paper　takes　RC　columns　as　the　research　object　and　performs　incremental　dynamic　analysis　(IDA)　on　the　actual　recorded　mainshock-aftershocks　(MS-AS).　The　Park-Ang　model　and　incremental　damage　index　are　used　to　quantify　the　effect　of　the　MS　and　AS,　respectively.　The　damage　and　fragility　analysis　of　the　parameters　such　as　reinforcement　ratio,　axial　compression　ratio　and　shear-span　ratio　are　carried　out　respectively.　The　results　show　that　the　seismic　demand　of　the　MS-AS　is　greater　than　the　MS.　Besides,　the　damage　of　the　column　gradually　increases　with　the　increase　of　axial　compression　ratio　and　shear-span　ratio,　and　gradually　decreases　with　the　increase　of　the　reinforcement　ratio.　When　the　seismic　design　grade　is　7,　8,　and　9　degree,　the　maximum　increase　rate　of　additional　damage　caused　by　aftershocks　is　7,　13,　and　15%　of　the　MS,　respectively.　When　the　column　is　in　a　medium　damaged　and　a　severely　damaged　state,　the　growth　rate　of　additional　damage　can　be　estimated　to　be　12.7　and　11%　of　the　MS,　respectively.　The　fragility　of　columns　in　different　damage　states　under　the　action　of　MS-AS　is　greater　than　that　of　MS.　Reducing　the　axial　pressure　ratio　can　greatly　reduce　the　damage　probability　of　columns　in　different　damage　states.　The　effect　of　the　MS-AS　can　be　comprehensively　considered　to　select　appropriate　design　parameters　in　the　design,　and　the　additional　damage　caused　by　the　AS　can　be　estimated　according　to　the　damage　condition　of　the　column.