Abstract: Limited by the shape of the excavation which cannot form an effective arch, there are extremely high requirements for deformation control during the tunneling of large section flat-top straight wall section tunnel. Through the Wukesong underground parking garage-underpass-intermediate pedestrian passage under the subway line 1 project, the deformation law of the tunnel under the existing subway structure is analyzed, and relevant concepts and measures to control the existing structural deformation are proposed. Measures are adopted to control the deformation, such as advanced deep hole grouting, multiple support of primary lining, dynamic grouting, and structural displacement control. The deformation of existing subway structures was successfully controlled within 3 mm, ensuring the structural safety and operational safety of subway. The increase of the stiffness of the elastic foundation beam, the control concept of the existing structural displacement distribution and the above-mentioned related measures can effectively control the deformation of the existing structure during the construction of the large section flat-top straight wall tunnel, and provide reference for similar projects.