Abstract: In order to improve the seismic performance of tunnels crossing active faults, starting from the energy response of structures, the factor of fault misalignment is introduced, the theory for calculating the energy response of tunnels crossing active faults under the action of earthquakes is optimized, and the method for calculating the energy response curve of the tunnels under the action of earthquakes and fault misalignment is put forward according to the relationship between the input energy and the intrinsic energy of the structures. Thus the method for distinguishing the zone of seismic damage impacts in the tunnels crossing active faults is established, and it is applied in the researches on the active fault section of F5 of the Longdongzi Tunnel. The results show that the destabilisation damage of the F5 active fault segment occurs around 10 s after the earthquake, with the maximum damage rate of 58%. The seismic impact zones for the tunnels crossing active faults are partitioned based on the damage rate, Through the analysis of the seismic damage information of the F5 active fault section of Longdongzi Tunnel and the F8 active fault of Longxi Tunnel set in Wenchuan Earthquake, the type and distribution of seismic damages on the site are more consistent with the proposed seismic impact zones. It is shown that the seismic impact zone method for the tunnels crossing active faults based on the energy principle can be used in engineering practice. The research results can provide an reference for the anti-seismic design of tunnels crossing active faults.