To study the influence of dense floor openings on existing main structures of subway stations, based on the reconstruction and expansion project of Dongsi Shitiao Station on Line 3 of Beijing Subway, finite element analysis method was used to simulate the dense openings on the bottom plate and the construction of vertical shafts. The stress and deformation characteristics of the station main structure were analyzed, and the impact of different phased opening schemes on the structural deformation of the station floor was discussed. Finally, verification was conducted in conjunction with on-site monitoring. The results show as follows. During the excavation and support process of shafts after floor opening, staggered excavation of adjacent shafts can effectively reduce the deformation of the station main structure, with the deformation being related to the depths of the two shafts and the distance between them. When the number of floor openings is large and dense, the opening order needs to be reasonably allocated. Through comparison and optimization of different phased opening schemes, it is found that compared to the three-phase opening scheme, the two-phase opening scheme increases the settlement by an average of 0.3 mm. However, the former shortens the construction period, improves construction efficiency, and is therefore recommended under the condition of meeting deformation control requirements.