The　modified　suction　caisson　(MSC)　adds　a　short-skirted　structure　around　the　regular　suction　caisson　to　increase　the　bearing　capacity　and　limit　deflection.　In　this　study,　the　undrained　pullout　capacity　of　MSC　in　nonhomogeneous　clay　with　shear　strength　increasing　linearly　with　depth　was　investigated　using　the　finite　element　limit　analysis.　An　implicit　dimensionless　pullout　bearing　capacity　factor　N＇　MSC　was　proposed　by　considering　the　effects　of　adhesion　factor　α　of　the　soil–suction　caisson　interface,　embedment　ratio　d/l,　diameter　ratio　D/d,　and　embedded　length　ratio　L/l.　Results　indicate　that　the　MSC　can　effectively　provide　a　higher　undrained　pullout　capacity.　The　N＇　MSC　tends　to　increase　with　increasing　the　embedment　ratio　d/l,　diameter　ratio　D/d,　and　embedded　length　ratio　L/l,　and　to　decrease　with　increasing　the　adhesion　factor　α　of　the　soil–MSC　interface.　A　theoretical　method　of　calculating　the　pullout　capacity　of　the　MSC　was　also　proposed　in　terms　of　the　vertical　static　force　equilibrium.　©　2017,　©　2017　Taylor　&　Francis.