Abstract: A constitutive relationship model for rectangular concrete-filled steel tube columns with binding bars (rectangular CFT-WB) is developed based on the constitutive model for square CFT-WB and the analysis of mechanism of rectangular CFT-WB. The constitutive model considers the difference between concrete confinement effect provided by broad faces and that provided by narrow faces of the steel tube and the difference in the binding bar arrangement in different directions. The failure criterion for concrete based on true triaxial compression test is used to predict the ultimate strength of concrete core. The parameters of the model are calibrated against the test results. Finally, a calculation of complete load-stress relationship curves is conducted for some certain experimental specimens using this constitutive relationship. The comparison between the results of calculation and those of corresponding test shows that they agree well with each other.