A comparative study on aseismic performances of different base isolators for multi-span continuous bridge is carried out. The laminated rubber bearing and the resilient-friction base isolator are considered. Nonlinear time-history analyses for several earthquake excitations using finite element program are performed. The accelerograms of the N00W component of El Centro 1940 and the N90W component of Mexico City 1985 earthquakes are used as earthquake ground excitations. The displacements of the deck, the deformations of the piers, the shear forces and the bending moments of the lower ends of the piers are obtained. The seismic responses of isolated bridges by the laminated rubber bearing and by the resilient-friction base isolator are compared with those of a bridge using conventional pot bearings. The results show that base isolation systems are highly effective in reducing the magnitude of the forces transferred to the substructure of the bridge. The aseismic performance of the resilient-friction base isolator is better than that of the laminated rubber bearing. Furthermore, the resilient-friction base isolator is less sensitive to unexpected variations in frequency content of the ground excitation.