Abstract: In view of the current practical problems of neglecting the existence of underground diaphragm walls in the study of seismic performance for underground subway structures, a static and dynamic coupling finite-element model for the interaction system of soil-diaphragm wall-complicated unequal-span subway station is established, and the earthquake responses among the unequal-span subway station without diaphragm wall as wells as structures with single- and double-layer diaphragm walls are compared and analyzed. The results show that the existence of diaphragm walls can significantly improve the resistance of the station to horizontal lateral displacement in small earthquakes, while the horizontal displacement of the subway structures increases obviously when the seismic intensity increases. Moreover, the interlayer displacement of the lower structures increases the most, which implies that the calculated results of ignoring the existence of underground diaphragm walls will be skewed to danger. The diaphragm walls strengthen the anti-lateral stiffness of the subway station, which leads to a significant change in the overall deformation state and internal force distribution of the underground structures, among which the stress level at the end of the side wall of the structures is dramatically reduced and the stress level at the end of each floor is increased significantly. The lower columns of unequal-span subway station act as the weak position in the structural seismic design under strong earthquakes, especially for the case of double-layer diaphragm walls.