Centrifuge shaking table tests and three-dimensional numerical simulations of dynamic interactions among soil， foundation， and structure are conducted for both a traditional pile group foundation of bridge and a novel cushioned pile raft foundation of bridge in sand. By comparing the dynamic responses of the two kinds of foundations subjected to different peaks and types of earthquake waves， the seismic isolation mechanism of the cushioned pile raft foundation is discussed， and the influences of the thickness of cushion and other factors on the seismic response of the cushioned pile raft foundation are studied based on parameter analysis. The results show that when compared with the pile group foundation， the acceleration of the superstructure of the cushioned pile raft foundation decreases， while its peak and residual displacement increases. The constraint of pile head is weakened， and sliding takes place between the raft and the interposed layer in strong earthquakes， thus reducing the inertial force transmitted to the foundation， which leads to a decrease of the maximum pile bending moment and a moving down of the position of the maximum pile bending moment. The pile bending moment increases significantly with the decrease of the thickness of cushion.