Abstract: Cold-formed steel box shape section has the special features both its mass center and moment center beingunified as double symmetry section and its outstanding advantage in moment and torsion rigidity. This paper presentsa new kind of cold-formed steel box shape composite sections, that is flanges opposite being welded to form acomposite section DS. The mechanical properties such as buckling modes, load carrying capacity, rigidity, ductilityand correlation curves of new section members subjected to axial compression, flexure, combined compression andbending were analyzed by using nonlinear finite element method. The consumed steel quantities of per unit loadcarrying capacity between new section members and the same section dimensions of cold-formed C-section memberswere also compared systematically. Some conclusions could be drawn from above work that the DS section membershad some superiority properties such as higher load carrying capacity and section modulus especially subject tocompression load, sufficient section stiffener and difficult for the sub element local buckling to happen and so on.They were very suitable to carry compression, and flexure loads, and combined compression and bending load, too.The consumed steel quantities were almost 50% as the same dimension C-section compression members. The DSsection members could go deep into the experiment study as to be used in the practical projects.