Abstract: FE models of composite-sectioned square concrete filled steel tube(CFST) stub columns were established in this paper.It was found that the calculated axial bearing capacities and load-deformation curves agreed with those of measured data well.The composite-sectioned CFST stub columns had excellent ductility and high residual bearing capacity with the constraint of square and circular steel tubes under compression.The mechanical behaviour of the square and circular steel tubes and core concrete were analysed under compression.The measured and calculated results show that,the increase of bearing capacities of the composite columns changes with the increasing diameter of the inner circular steel tubes,that is,the changes increase at first,then decrease.