Abstract: Plentiful experiment researches and the finite element analysis are performed on short and slender columns under axial compression beams, short columns and slender columns under eccentric compression, short columns and slender columns of high-strength concrete filled square steel tube with inner CFRP circular tube under bi-axial eccentric compression. The failure mode and the mechanism of all kinds of members in an entire process are analyzed. And a simplified formula calculating the bearing capacity for each member is proposed. On the basis of above, the comparison between this new composite structure and a traditional concrete filled square steel tubular structure is done.