It has long been recognized that energy input, absorption, and dissipation in seismic resistant design of structures are the most fundamental quantities controlling seismic performance. While the input energy($E_I$) is a reliable parameter for selecting the most demanding earthquake ground motion, it alone is not sufficient for proper seismic design of the structure. The importance of reliable estimation of the input energy of possible earthquake ground motions at the site of structure in order to select the proper design earthquake motion is emphasized. This paper discusses the characteristic of input energy concepts between the real recorded ground motion and the artificial ground motion in seismic resistant design of building structures. For long-period contents dominant earthquake ground motion, the input energy spectra are sensitive to the variation of the natural period of structures. It is concluded that the input energy quantities by the artificial ground motions used in this paper presented better stability than those by real recorded ground motions. Also, the artificial ground motions compatible with design spectrum are applicable as input ground motions for a seismic response analysis of building structures.