A simple analytical method of seismic response of seismically isolated bridges is presented. Poundings of two decks and between deck and abutment are considered in this analysis. Impact spring model is used to represent impact force for displacement between decks or deck and abutment In this model, shock absorber made of natural rubbers and steel cables which join decks to adjacent deck or abutment are considered. Analytical model in this method consists of some five-degree-of-freedom-systems with four masses, which are connected in series. From analytical results, it is found thatsimple analytical method proposed here is useful to examine the effect of pounding on non-linear seismic response of each part of bridges and also investigate adequate clearance and characteristics of shock absorber and connection cable to mitigate the pounding effect.