Abstract: To clarify the influence of construction joints on the structural safety of operating tunnels in water-rich condition, taking a typical railway tunnel defects as the basis this paper uses the FLAC3D software to establish a simulation analysis model, and studies the influence laws of the internal forces, safety coefficients and deformation patterns of the lining structures with/without construction joints and under different groundwater heights. The research results show that the occurrence of the tunnel defects is not only due to the rising of the groundwater level caused by concentrated rainfall on the ground surface, but is also significantly related to existing defects (construction joints) in the lining structure; the existence of construction joints will not only change the original bearing mode of the lining, resulting in the significant increase of the axial force at the side of the construction joints and abrupt change of the bending moment, but also change the deformation mode of the lining structure, in which case the lining structure would be prone to misalignment slip along the surface of construction joints, and part of the lining structure would be bent inward, causing deformation damage.