Abstract: The pier of common bridge in mountain areas can be easily damaged under rock-fall impact due to its high stiffness. However, there is lack of effective measures to protect it. Based on the study of elastic-plastic mechanism of rock-fall impact on pier, and according to energy dissipation theory, an elliptic structure with two cavities filled with aluminum foam is proposed. By combining the MTS test resutls, the dynamic response and optimized design of the new structure is analyzed by dynamic finite element method. The results show the elliptic structure wrapping up pier eccentrically can weak impact efficiently and enhance system safety economically. Meanwhile, the thicker aluminum foam layer would dissipate more impact energy. However, when the layer is too thick, large rigidity of structure is induced. In addition, among the different filled modes, the structure with a thin outer layer and filled with large intensity aluminum foam can control plastic deformation and pier deflection very well. The new structure can keep the safety by weakening the impaction and dissipating energy significantly.