In　order　to　study　the　working　mechanism　of　rectangular　steel-concrete　composite　columns　subjected　to　compression-bending　load　and　further　determine　the　seismic　performance　index,　a　bottom　strengthened　rectangular　steel　reinforced　concrete　(SRC)　column　with　concealed　steel　plates　and　a　bottom　strengthened　rectangular　concrete　filled　steel　tube　(CFST)　columns　were　proposed.　Six　column　models　with　different　configurations　were　tested　under　horizontal　low　cyclic　loading.　Based　on　the　experiments,　the　load-bearing　capacity,　stiffness　and　degradation　process,　ductility,　hysteretic　energy　dissipation　capacity,　and　failure　characteristics　of　the　models　were　analyzed.　The　load-bearing　capacity　calculation　formulas　for　a　normal　section　and　an　oblique　section　of　bottom　strengthened　rectangular　steel-concrete　composite　columns　were　pesented　and　a　finite　element　(FE)　numerical　simulation　of　the　classical　specimens　was　performed.　The　study　shows　that　the　load-bearing　capacity,　ductility,　and　seismic　energy　dissipation　capacity　of　the　bottom　strengthened　rectangular　steel-concrete　composite　columns　are　significantly　improved　compared　to　the　conventional　rectangular　steel-concrete　composite　columns　and　the　results　obtained　from　the　calculation　and　the　FE　numerical　simulation　are　in　good　agreement　with　those　from　the　experiments.　The　rectangular　steel-concrete　composite　column　with　bottom　strengthened　shows　better　seismic　behavior　and　higher　energy　dissipation　capacity　under　suitable　constructional　requirements　and　it　can　be　applied　to　the　structure　design　of　high-rise　buildings.