In　this　paper,　issues　related　to　the　vertical　seismic　responses　and　P-delta　effects　of　the　base-isolated　buildings　are　discussed.　Taking　a　frame　structure　as　an　example,　the　isolated　layer　was　firstly　designed　according　to　the　code　for　the　seismic　design　of　buildings　6(GB　50011-2001),　and　then　the　displacement　responses,　the　acceleration　responses　and　the　story　shear　forces　of　the　frame　structure　are　compared　with　those　of　the　base-isolated　frame　structure　under　common　earthquakes.　It　is　verified　that　the　base　isolation　technology　is　effective　in　decreasing　the　horizontal　responses　of　the　structure.　Finally,　the　internal　forces　of　the　columns　in　the　basement　are　studied　for　several　cases　such　as　not　considering　the　vertical　seismic　responses　and　P-delta　effects,　only　considering　the　P-delta　effects,　and　considering　both　the　vertical　seismic　responses　and　P-delta　effects　under　seldom　earthquakes.　It　is　found　that　both　the　vertical　seismic　responses　and　P-delta　effects　have　some　influence　on　the　internal　forces　of　the　columns　in　the　basement　when　the　seldom　earthquakes　occurs.