To enhance the earthquake resistance capacity of long-span continues bridge, theory and design of a new seismic isolating system are proposed based on the utilization of improved carbon structural steel material. Pseudo-static test result of the damping tenon, one essential energy dissipation component, proved the system’s excellent characteristic of consuming earthquake energy. Comparative experiments of three models reflect the working stability of the damping tenon confronted with different stimulation. Finite Element simulation further validates accuracy of the experiment and helps analyzing the material’s elastic and plastic developing status due to different load steps. Finally, this new seismic isolating system is recommended to long-span continues girder bridge designed on the basis of high level earthquake resistant standard.