The seismic design requirements in the Building Standard Law of Japan were revised in June 2000 to a performance-based design framework.A new seismic design method called the "Response and Limit Strength Calculation"(RLSC),which incorporates the effect of nonlinear amplification of surface strata and soil-structure interaction,was developed.The Nonlinear amplification Gs of the surface strata is computed by the response spectrum method,however,it is not applicable to the soil liquefaction.This paper describes the response spectrum method considering soil liquefaction using "Recommendations for design of building foundations" edited by Architectural Institute of Japan.The results of this extended response spectrum method is verified by the one-dimensional equivalent linear analysis SHAKE and the one-dimensional effective stress response analysis DESRA.