Existing problems of capacity-demand diagram were considered, and the conversion method between the results of the capacitydemand curves method and dynamic time-history analysis is presented. The factors causing the relative error between the different capacity curves, such as the distribution type for lateral load, assumptions of member bar model , surface irregularity of the structures and P-△ effects, were analyzed to build the statistical correlation between the maximum base shear and the top displacements of the components under the different pushover analysis. ATC-40 (Procedure-B) method is verified to be more accurate in calculating the roof displacements of buildings. Meanwhile, the improved method is refined in three aspects and proved effective by a real concrete-frame building.