Abstract: Objective At present, in the engineering of 9-meter-class large-diameter city railway shield tunnels,there are no documented cases of link passages constructed using machinery methods with eccentric openings yet. Therefore, it is necessary to investigate their seismic performance under earthquake loading conditions. Method Based on a city railway link passage project, a numerical model is developed using finite element software Plaxis 3D for simulation analysis of the main tunnel-link passage structure seismic performance under horizontally incident seismic waves, which are perpendicular to the link passage direction. Result ＆ Conclusion For the combined structure of large-diameter main tunnel and link passage, the axial force and bending moment at the joint section vary significantly. Under seismic waves with a peak acceleration of 0.1g, the maximum axial force increases by 53% compared to the initial condition, and the bending moment increases by 410%, both located at the tunnel arch waist. In contrast, internal force variations at link passage mid-section are relatively minor, with a maximum increase amplitude of less than 30% in sectional internal forces. Due to the constraint effect of the main tunnel, both the absolute displacement and the convergence deformation at the main tunnel-link passage junction are significantly smaller than those at the link passage mid-section. Under seismic waves with a peak acceleration of 0.2g, the additional convergence deformation at the joint section is-0.25 mm, while at the link passage mid-section it is 0.59 mm. Under the action of horizontally incident seismic waves, the link passage mid-section experiences an inclined elliptical deformation, with the maximum displacement points located at the 45° and 135° positions of the upper semicircle, with an inclined additional convergence deformation of 1.56 mm.