To adopt the constitutive relationship of square CFT with binding bars, nonlinear analysis method of the whole process curve of capacity-deformation of square CFT stub columns with binding bars subjected to eccentric loading is carried out based on fiber model method. The analysis results are in good agreement with the experimental ones. The parameters analysis of the curvature ductility of the CFT stub columns subjected to uniaxial and biaxial eccentric loading are performed by using verified programs, simplified formulas to calculate curvature ductility of square CFT with binding bars are regressed, which have high accuracy and simple expression.