Near-field　and　far-field　long-period　ground　motions　are　featured　by　rich　long-period　components　or　near-field　pulse　components,　which　may　result　in　the　excessive　deformation　of　the　isolation　layer.　Its　adverse　influence　on　the　seismic-reduction　performance　of　the　high-rise　isolated　structures　should　be　revealed　and　validated　by　shaking　table　test.　To　this　end,　the　response　spectrum　characteristics　of　near　and　far　field　ground　motions　are　analyzed.　Then,　a　single-tower　steel　frame　structure　with　a　large　chassis　is　designed　to　form　a　typical　test　model.　One-dimensional　shaking　table　test　and　numerical　simulation　are　performed.　Also,　the　impacts　of　long-period　ground　motions　on　the　seismic-reduction　performance　of　story　acceleration　and　interstory　drift　are　investigated.　Further,　in　view　of　the　possible　excessive　displacement　of　the　isolation　layer,　a　combined　seismic　mitigation　and　isolation　system　is　proposed　by　adding　viscous　dampers　on　the　isolation　layer.　The　effectiveness　of　the　seismic　mitigation　and　the　limit　protection　are　analyzed　and　verified.　The　results　show　that　when　compared　with　the　conventional　ground　motions,　the　response　of　isolated　structures　will　be　larger　under　the　far-field　long-period　ground　motions.　When　subjected　to　near-field　pulse　long-period　ground　motions,　the　seismic-reduction　effect　of　the　structure　get　worse　and　the　maximum　displacement　of　isolation　layer　is　far　beyond　the　allowable　displacement.　Besides,　the　combined　seismic　mitigation　and　isolation　system　can　effectively　control　the　maximum　drift　of　the　isolation　layer　and　reduces　the　acceleration　and　interstory　drift　response　of　the　large　chassis.　It　also　have　well　seismic-reduction　effect　on　the　upper　tower.　©　2017,　Nanjing　Univ.　of　Aeronautics　an　Astronautics.　All　right　reserved.