Based on the research background of the shield tunnel in a parking lot of an urban subway, According to the construction conditions of the new tunnel passing through the existing tunnel, the vertical displacement of the existing shield tunnel in the middle and lower part of the construction is simulated by numerical simulation, and the tunnel deformation value after grouting reinforcement of the existing tunnel is analyzed, Finally, the reinforcement suggestions are put forward. The analysis results show that the excavation of the left line and the right line of the new tunnel has a great difference in the impact on the existing tunnel. At the same time, the crossing angle of the upper tunnel affects the settlement displacement of the existing tunnel. The vertical displacement of the existing tunnel segment directly below the construction tunnel line is 5.3 mm larger than that of the tunnel segment diagonally below. The simulation results show that the maximum deformation of the strengthened tunnel decreases from 3.2 mm to 4.5 mm, which is less than 5 mm of the standard control safety standard. On this basis, a tunnel reinforcement scheme combining steel support ring and arch crown grouting is proposed, and the on-site construction is guided.