The　paper　presents　experimental　study　on　an　improved　plate　lead　shear　damper　with　long　stroke　(ILSD-LS)　which　is　developed　to　meet　the　engineering　requirements　for　high-rise　structures　with　long　periods　subjected　to　the　long-period　earthquakes.　Finite　element　analysis　is　also　carried　out　to　investigate　the　proposed　damper.　Based　on　the　ideal　rigid-plastic　constitutive　law　of　lead,　a　mechanical　model　of　the　ILSD-LS　is　established.　Compared　with　ordinary　dampers,　ILSD-LS　has　better　damping　force,　energy　dissipation　capacity,　and　stability　according　to　the　results　of　simulation　and　experiments.　The　method　of　calculating　damping　force　is　reasonable　and　accurate.　In　order　to　verify　the　damping　effect　of　ILSD-LS　for　the　structures　with　long　periods　under　long-period　ground　motions,　the　nonlinear　time　history　analysis　of　a　typical　high-rise　structure　with　ILSD-LS　is　carried　out.　The　numerical　results　indicate　that　the　seismic　responses　of　the　high-rise　structure　with　ILSD-LS　are　significantly　reduced　when　subjected　to　long-period　ground　motion.