In order to study the impact of deep foundation pit dewatering construction on adjacent existing metro shield tunnels, a deep foundation pit dewatering project adjacent to a metro line is studied with numerical simulation, theoretical analysis, and on-site monitoring data comparison to systematically analyze the influence characteristics of the dewatering process of the deep foundation pit on adjacent metro structures. The results indicate that: (1) The settlement values of soil layers at all monitoring points exhibit a distribution characteristic of “maximum at the surface, gradually decreasing with depth,” with consistent settlement trends across different monitoring points; (2) In surface settlement monitoring, the maximum settlement value (13.58 mm) was recorded at Point A, while the minimum settlement value (9.02 mm) was recorded at Point F; (3) The settlement values of soil layers at the burial depth of the metro shield tunnel range from 3.57 to 5.43 mm, indicating minimal settlement and indicating that the impact of foundation pit dewatering on the metro shield tunnel is within a controllable range and meets relevant code requirements; (4) The trends of layer settlement data at all monitoring points align closely with theoretical analysis results, demonstrating good fitting and verifying the reliability of the theoretical analysis method. The findings of this study can provide theoretical support and practical references for the design of dewatering schemes, risk control, and deformation protection decision-making in deep foundation pit projects adjacent to metro lines.