The portal section of Feixianguan Tunnel is taken for an example to study the dynamic response characteristics and seismic resistance/reduction measures of tunnel portal section covered by thick loose deposits and crossing softhard interface. Three conditions are established by finite difference software, including progressive grouting measures, fullring grouting measures and setting shock absorption joints. By comparing stress and deformation of tunnel lining under the condition of no measures, the optimum seismic resistance/reduction measures are obtained. The results show that: (1) The longitudinal deformation of lining is far less than transverse deformation under strong earthquake, and the effect of fullring grouting on limiting the lateral deformation of lining is the most significant, while setting shock absorption joints separately tends to be poor effective. (2) The right arch foot and the right arch waist are the most dangerous locations for structural damage under strong earthquake, thus emphasis should be laid on strengthening the seismic reinforcement at these two locations. (3) Fullring grouting can effectively reduce lining stress, and it can make the stress change near the interface continuous and stable meanwhile.