Abstract: A response spectrum method was proposed for the seismic analysis of structural seismic force responses to multi-support excitations. Instead of partitioning the total structural response into the pseudo-static and dynamic components, the absolute displacement formulation was directly utilized in the method and thus the response spectrum combination rule was simplified for multi-support excitations. The seismic response of a structural example was studied, whereby a good agreement between the results of the time history method and the proposed method showed the validity of the latter method.