The　structural　dynamic　behavior　and　yield　strength　considering　both　ductility　and　strain　rate　effects　are　analyzed　in　this　article.　For　the　single-degree-of-freedom　(SDOF)　system,　the　relationship　between　the　relative　velocity　and　the　strain　rate　response　is　deduced　and　the　strain　rate　spectrum　is　presented.　The　ductility　factor　can　be　incorporated　into　the　strain　rate　spectrum　conveniently　based　on　the　constant-ductility　velocity　response　spectrum.　With　the　application　of　strain　rate　spectrum,　it　is　convenient　to　consider　the　ductility　and　strain　rate　effects　in　engineering　practice.　The　modal　combination　method,　i.e.,　square　root　of　the　sum　of　the　squares　(SRSS)　method,　is　employed　to　calculate　the　maximum　strain　rate　of　the　elastoplastic　multiple-degree-of-freedom　(MDOF)　system　under　uniform　excitation.　Considering　the　spatially　varying　ground　motions,　a　new　response　spectrum　method　is　developed　by　incorporating　the　ductility　factor　and　strain　rate　into　the　conventional　response　spectrum　method.　In　order　to　further　analyze　the　effects　of　strain　rate　and　ductility　on　structural　dynamic　behavior　and　yield　strength,　the　cantilever　beam　(one-dimensional)　and　the　triangular　element　(two-dimensional)　are　taken　as　numerical　examples　to　calculate　their　seismic　responses　in　time　domain.　Numerical　results　show　that　the　permanent　displacements　with　and　without　considering　the　strain　rate　effect　are　significantly　different　from　each　other.　It　is　not　only　necessary　in　theory　but　also　significant　in　engineering　practice　to　take　the　ductility　and　strain　rate　effects　into　consideration.