Abstract: Establishing a simplified applicable design input energy spectrum is the basis of applying the energy method to practical engineering design and verification. This paper has chosen 694 horizontal seismic records on classⅠ,ⅡandⅢ sites, and analyzed energy spectrum with different classification of design earthquakes and site classes. The correlation between 12 different ground motion parameters and the energy spectrum is examined, and a ground motion parameter among them having strong relation with ground motion input energy is selected. Based on the provisions of fortification intensity and security standard in the present code, a new parameter of classification of design earthquake is put forward and the corresponding design input energy spectrum for damping ratio of 5% of the elastic single degree of freedom system is built. Furthermore, some valuable recommendations for using the energy-based design method and selection of input ground motion are proposed.