In　this　study,　a　novel　two-stage　plastic-state　detection　strategy　is　studied.　In　the　first　stage,　discrete　wavelet　transform　(DWT)　is　used　to　obtain　the　low-frequency　response　signal.　The　Hankel　matrix　is　constructed　with　a　low-frequency　response　signal,　and　singular　value　decomposition　(SVD)　is　used　to　divide　the　null　space　and　non-null　space.　The　index　degree　of　nonlinearity　(DoN)　was　proposed　for　plasticity　detection,　and　the　corresponding　limit　of　linearity　(LLI)　was　constructed.　In　the　second　stage,　based　on　DWT　and　fast　independent　component　analysis,　normalized　source　distribution　vector　(NSDV)　was　proposed　to　locate　the　structural　damage.　The　method　was　verified　by　numerical　simulation　and　a　three-story　frame　test.　The　results　show　that　when　the　structure　is　in　an　elastic　state,　DoN　is　less　than　LLI;　when　the　structure　enters　the　plastic　state,　DoN　is　larger　than　LLI　and　increases　with　the　enhancement　of　plastic　degree;　thus,　the　proposed　index　NSDV　can　locate　the　structural　damage.　The　proposed　method　can　be　used　for　structural　plasticity　detection　and　damage　location,　and　has　strong　robustness　and　engineering　practicability.