An　equivalent　continuum　model　of　an　isogrid　structure　is　utilized　to　analyze　the　impact　response　of　isogrid　structures　and　stiffened　structures.　The　parameters　of　the　equivalent　model　are　determined,　and　the　comparison　between　the　equivalent　continuous　structure　and　the　real　grid　structure　are　examined　to　validate　the　reliability　of　the　equivalent　model.　Then,　the　impact　responses　of　stiffened　cylindrical　shells　with　and　without　an　elliptical　hole　are　investigated　by　using　the　equivalent　model　of　grid　structures.　For　a　different　location　and　geometry　of　the　elliptical　hole,　the　deformation　and　load-bearing　capacity　of　the　grid-stiffened　cylindrical　shells　are　studied.　The　numerical　results　indicate　that　the　present　equivalent　model　can　be　applied　effectively　in　simulation　for　the　impact　behavior　of　the　grid　and　stiffened　structures.　This　work　provides　a　comprehensive　understanding　for　the　impact　performance　of　the　complicated　stiffened　cylindrical　shells.　Copyright　©　2015　Tech　Science　Press.