Abstract: Structural dynamic stability is an important aspect of structural seismic performances. When earthquake happens, a relative motion would occur between girders and piers of the isolated bridge, and the eccentric force suffered by piers would increase, therefore, dynamic stability of isolated bridges subjected to earthquake should be analyzed. In this paper, the principle of dynamic stability was discussed and the elastic dynamic stability of isolated bridges subject to earthquake was studied using the combination of time-history. Eigenvalue bucking analysis was illustrated through the example of Dongjiang bridge, which is a double- layer-pier approach bridge with double traffic double LRB isolated continuous girders. 8 conditions of stability and initial eccentricity caused by temperature were considered. The results showed that: although the fixed pier is replaced by the isolated bearing, the dynamic stability under earthquake is improved because the deformations of piers become small.