The paper presents a case study to investigate the performance of deep excavation induced by existing adjacent metro stations. The engineering background involves an existing metro station adjacent to the deep excavation of a station pit for Line No. 18 of the Chengdu Metro. A 182-m-long, 28-m-wide, and 47-m-deep excavation was conducted adjacent to the existing metro station. Within this context, the deformation mechanisms of the deep excavation and reinforcement structure were systematically investigated and analyzed. The numerical simulation is addressed to analyze reinforcement parameters and to evaluate the unreinforced condition and three distinct reinforcement structures. A combined lateral and basal grouting scheme forming an “L”-shaped grouting-reinforcement structure was ultimately selected. This structure is designed to isolate vertical and horizontal components, thus effectively obstructing or attenuating the transmission of ground deformation. Consequently, surface subsidence is reduced and the soil-bearing capacity is increased. Based on the engineering monitoring data of excavation adjacent to the existing station, a 61.44 % reduction in lateral displacement of deep retaining wall piles at the mid-long side of the excavation, a 65.89 % decrease in ground surface settlement around the mid-long side, and a 66.42 % mitigation of differential settlement across both sides of the existing station were achieved. A comparative validation was conducted between field monitoring data and numerical simulation results at corresponding locations, demonstrating close agreement with all discrepancies within 5 % threshold. This study offers valuable insights and guidance for future deep-excavation projects.