This paper proposed a theoretic model to analyze the dynamic behavior of a bridge by applying the concept of rocking pier system (RPS) . Numerical analysis was proceeded to investigate the performance of the RPS under various circumstance such as with or without tendons, with slack or post-tensioned tendons, tendon areas, vibrating period of piers, and exciting intensity of 1940 El Centro earthquake. The calculated results indicate that a peak base shear at the bottom of piers may be produced, when impacts occur. However, this value is still smaller than that of a conventional pier system (CPS). So that the merit of RPS is to remain elastic and to avoid any damage under the excitation of strong earthquake. And the seismic intensity to start the rocking of RPS can be set by adjusting the tendon area or post-tensioned forces in order to prevent rocking and termination of transport function of bridges under excitations of smaller intensity of earthquakes.