Abstract: Aiming at the issue that safety accidents are prone to occur during the close-proximity construction of small clear distance over-passing tunnels due to the unloading effect, it focuses on a newly-built gas tunnel project of over-passing existing shield tunnel. A three-dimensional numerical model is established using Midas GTS NX to analyze the influence of the newly-built gas tunnel construction on the structural displacement and stress changes of the existing shield tunnel. Additionally, displacement and deformation monitoring is carried out on the section of the existing shield tunnel affected by the construction. The comparative analysis of the simulation results and on-site monitoring data shows that the measured values are generally lower than the numerical simulation results, and the displacement values are far below the safety control criteria. It indicates that the structure of the existing shield tunnel remains safe and controllable under construction disturbances.