This paper deals with the 3-D finite element deformation analysis of concrete-filled tubular (CFT) steel columns subjected to monotonic loading. The finite element package program, DIANA is used to carry out the verification analysis. As for the constitutive model of materials, the Drucker-Prager model in DIANA is applied as the concrete material. This model has the features such as the linear tension cut off in tension range, the compressive softening behavior in compression range and the confining effect on concrete strength. The multi-linear constitutive material model is used as the steel material, and the interface element is used to represent the gap and contact behavior between steel and concrete. The 3-D FEM analysis on monotonic behavior of concrete-filled tubular (CFT) steel columns is investigated by comparing the analytical results with experimental results.