In　order　to　consider　P-Δ　effect　and　rotation　of　isolation　bearings　existing　in　the　serially　isolated　system　with　laminated　rubber　isolation　bearings　and　cantilever　columns　in　basement,　mechanics　model　of　this　serially　isolated　system　was　established,　and　the　associated　frequency　equation　was　derived.　Then,　the　frequencies　and　the　modes　were　solved　by　using　a　numerical　method.　Based　on　Betti＇s　theorem,　the　generalized　mass　and　the　stiffness　of　the　serially　isolated　system　considering　P-Δ　effect　and　rotation　of　isolated　bearings　were　presented,　and　the　response　of　the　serially　isolated　system　were　obtained　by　the　mode　superposition　method.　Finally,　a　practical　isolated　building　was　chosen　as　the　example　structure　to　analyze　the　seismic　response　and　the　effect　of　the　parameters.　The　results　show　that　the　novel　method　considering　P-Δ　effect,　rotation　of　isolation　bearings　and　deformation　of　cantilever　columns　can　solve　the　deformation　of　cantilever　column,　rotation　angle　at　the　top　of　cantilever　column　and　seismic　response　of　the　structure.　When　the　ratio　of　the　horizontal　stiffness　of　the　cantilever　column　to　the　isolation　bearing　is　small,　the　difference　of　seismic　response　between　serially　isolated　system　and　isolated　system　with　rigid　joint　at　the　bottom　of　bearings　is　significant,　and　with　the　increase　of　the　ratio　of　horizontal　stiffness　of　the　cantilever　column　to　the　isolation　bearing,　the　difference　will　become　smaller　rapidly,　then　the　section　of　cantilever　column　can　be　determined.　The　vertical　stiffness　of　the　isolation　bearing　should　be　as　large　as　possible　to　decrease　the　rotation　angle　of　the　bearings.　When　the　joint　of　bearing　and　the　cantilever　column　of　the　serially　isolated　system　can　be　taken　as　rigid　joint　to　calculate　the　seismic　response　of　structure,　the　P-Δ　effect　only　have　large　influence　to　the　response　of　the　cantilever　column,　which　indicates　the　P-Δ　effect　should　be　considered　in　calculated　response　of　the　cantilever　column.　©,　2015,　Tumu　Gongcheng　Xuebao/China　Civil　Engineering　Journal.　All　right　reserved.