Abstract: This paper takes the project of Tianjin Metro shield cutting the existing station's diaphragm walls as the background. Through on-site monitoring, theoretical analysis and other methods, it deeply studies the variation laws of the vertical displacements of the surface and the station during the process of shield cutting the existing station's diaphragm walls. The research results show that before the shield cuts the diaphragm wall, the vertical displacement of the surface is small and basically stable. After the shield cuts the diaphragm wall, the vertical displacement of the surface changes significantly, and its variation law is closely related to factors such as the rotation direction of the shield machine, the relative position between the diaphragm wall and the shield tunnel, and stratum reinforcement. By taking measures such as stratum improvement and reinforcement, optimization of shield tunneling parameters, synchronous and secondary grouting, and real-time monitoring and early warning, the vertical displacement of the station structure can be effectively controlled. In the construction of shield grinding the diaphragm wall, the correlation between the vertical displacements of the station structure and the surface is not significant. The research results of this paper provide a reference for the design and construction of similar projects, help to further improve the construction technology system of shield cutting the existing station's diaphragm walls, and promote the high-quality development of urban underground engineering construction.