This　paper　presents　a　novel　two-stage　damage　detection　method　by　integrating　modal　strain　energy　and　revised　particle　swarm　optimization　(RPSO).　In　the　first　stage,　the　modal　strain　energy　change　ratio　(MSECR)　is　used　to　roughly　identify　the　locations　of　damaged　elements　via　an　appropriate　MSECR　threshold　which　is　determined　through　parameter　estimation.　In　the　second　stage,　RPSO　that　integrates　evolutionary　theory　with　general　PSO　is　used　to　precisely　locate　and　quantify　the　damage　with　the　gravity　position　of　the　selected　excellent　particles　in　the　current　entire　population　taken　into　consideration.　Two　numerical　simulations　and　a　seven-story　steel　frame　experiment　in　laboratory　conditions　are　performed　to　validate　the　proposed　method,　and　a　comparison　is　made　between　the　proposed　approach　and　existing　methods.　The　results　show　that:　(1)　the　proposed　method　can　not　only　effectively　locate　damage,　but　also　accurately　evaluate　the　extent　of　damage.　Meanwhile,　it　also　enjoys　good　noise-tolerance　and　adaptability;　(2)　the　damage　threshold　of　the　MSECR　presented　in　this　paper　can　be　determined　by　the　parameter　estimation　and　reliability　index,　and　then　used　to　reduce　the　number　of　elements　to　be　analyzed　and　to　improve　the　computation　efficiency　in　the　second　stage;　and　(3)　compared　with　general　PSO　algorithm,　RPSO　is　more　efficient　and　robust　for　damage　detection　with　a　better　noise-tolerance.　This　study　shows　that　the　proposed　method　can　provide　a　reliable　and　fast　tool　to　accurately　identify,　locate　and　quantify　single-and　multi-damage　of　complex　engineering　structures.