Abstract: Seismic responses of two typical large-span structures to uniform vertical seismic excitation are investigated and the effects of multi-support vertical excitation on the responses are checked. Results indicate that uniform vertical seismic excitation causes relative large responses in both the trussed gable frame structure and the reticular dome supported by a substructure and thus it should be considered in the seismic design of these structures. When the effect of multi-support vertical excitation is taken into account, seismic responses of the gable frame structure are very close to those under the uniform excitation and thus the effect can be ignored in seismic design of such structures. Responses of the reticular dome are reduced by the effect of multi-support vertical excitation. Meanwhile, responses of the substructure of the dome changes a little since the pseudo-static component of multi-support excitation produces slight internal force in the substructure.