To evaluate the effects of internal structure and various construction methods of internal structure, including fully prefabricated and prefabricated + castinplace, on the transverse seismic performance of the entire shield tunnel structure, a refined threedimensional model of the stratumtubeinternal structure considering the Yellow river tunnel in Jinan, China, is established. Furthermore, the explicit dynamic time method is utilized to study the seismic performance. The results reveal the following: (1) The constraining effect of internal structure on tunnel deformation changes gradually. Moreover, during the elastic working stage, tunnel deformation is effectively reduced by increasing the contact surface connection stiffness, and the tunnel′s maximum radial convergence is reduced by 86.87%. During the plastic working stage, the deformation of the tunnel is intense due to the inertial force and gravity of the internal structure. (2) Considering the internal structure, the segment peak stress and damage in the application area of the internal structure is drastically reduced, the maximumminimum principal stress is reduced by 50.75%, and the maximum stiffness reduction factor is reduced by 0.060 6. (3) Considering the internal structure, the tunnel′s local axial force and bending moment is reduced. When the internal structure is prefabricated and cast in place, the bending moment is reduced by 769 kN·m, and the axial force by 1 798 kN. (4) The larger the stiffness of the contact surface between the internal structure and the segments, better the coordinated deformation ability of the two. Therefore, the weak area of the internal structure should also be reinforced synchronously to prevent the structure from entering the plastic working state too soon.