Abstract：Because the vertical stiffness of two kinds of bearings of parallel base isolation structures are different，the axial forces will shift when the displacement of isolation layer increases under earthquake loading；and the dynamic characteristic of isolation layer appears strong nonlinearity. According to the character of axial forces shift between two kinds of bearings under earthquake loading，the resilience model of isolation layer considering the vertical force is given；and the calculating model is studied too. A dynamic simulation method for the isolation system based on SIMULINK is put forward，in which the shift force between the rubber bearing and the sliding isolated bearing is considered. The results of an example show that the horizontal maximum displacement of isolation layer will decrease when the axial force transfer is considered. So the effects of additional friction forces caused by bearing vertical force transfer cannot be neglected.
