Abstract: Taking the No.2 tunnel of the Lot 3 of the Phase I project of Nariobi-Malaba Railway as the background, this paper uses the ANSYS software to conduct numerical modeling for the simulation study of the seismic response and seismic mitigation measures of tunnels under fault dislocation and seismic action. The results show that the seismic response of the tunnel sidewalls is the most obvious both under the action of fault dislocation in the vertical direction and the seismic action in the horizontal direction; fault dislocation leads to stress redistribution in the tunnel under the effect of gravity as well as seismic action, where the principle stress extreme value, X-displacement extreme value and maximum acceleration increase obviously, with the largest increase in acceleration; the seismic response of the tunnel under fault dislocation and seismic action decreases obviously with increasing of damping ratio of the shock mitigation layers, and a shock mitigation layer with larger damping ratio can effectively reduce the extent of increase in the stress, displacement and acceleration induced by the seismic response of the tunnel due to fault dislocation; sand-rubber mixture and gravel-rubber mixture, in combination with geocell reinforcement, are potentially suitable seismic mitigation materials for tunnels.