The foundation pit excavation has a significant impact on the deformation of retaining structure. PLAXIS 3D is utilized for numerical simulation in this paper based on the hardening model considering the small strain characteristics of the soil, combined on the foundation pit project of a subway station in Hangzhou. The influences of different excavation conditions on the deformation, axial force and surface settlement during construction are analyzed in detail. Results show that there is a significant deformation difference between the left and right sides of the retaining structure of the same foundation pit. The soil layer cannot be simply regarded as horizontally distributed soil layer during the process of analysis. The pile load of the soil on the side with large deformation should be reduced, as well as the load should be distributed on the side with small deformation of the retaining structure as far as possible. Meanwhile, the horizontal displacement, surface settlement, and deformation increase gradually with the foundation pit excavation and station construction. In addition, the deformation of the diaphragm wall is significantly affected by the excavation sequence of the foundation pit. The excavation from the middle to both sides has the smallest influence on the deformation of the retaining structure, only 18.35mm, which is about 25% less than the original condition, and has the most favorable influence on the project. The research results can provide a theoretical reference for the design and construction of subway foundation pit, and also have a good guiding significance for practical engineering.