The real stiffness of frame in different deformation phases was determined according to experimental data, and the stiffness degradation coefficient was adopted to revise the stiffness of each floor. By using the stiffness degradation coefficients of free vibration period, shear and lateral displacement, the structural behaviors were revised. A practical method for calculating the behaviors of frame structures considering the structural stiffness degradation was presented, and the calculation steps were given. An 8 storey frame was taken for the example, and the influence on the behaviors of t...