Abstract: In addition to the risk of reinforced concrete deterioration caused by corrosive seawater, the lining structure of a cross-sea tunnel is also affected by the formation load and by the water pressure outside the structure. To reveal the gradual deterioration process of a cross-sea tunnel lining under the combined action of water and soil pressure and, of chloride ion erosion, a numerical calculation model for the rust expansion failure process of a concrete lining of a subsea tunnel in a chlorinated erosion environment under hydraulic-mechanical-chemical coupling action is established by the grounds of the peridynamic model suitable for unstructured discrete grid. Combined with the Abaqus platform, the process of structural damage caused by the seawater erosion of the undersea tunnel lining under the coupling action of water, of chemical and, of force was numerically simulated. The results show that the rust expansion cracking mode of the lining presents significant regional characteristics. The large-scale parallel cracking of the concrete protective layer occurs on the outer side of the arch top and of the arch bottom, while the damage at the arch waist is relatively light. The vertical cracks induced by reinforcing bars tend to inclined and propagate towards the top or the bottom of the arch. Finally, the influence of different influencing factors on the rust failure of the lining concrete was discussed. Parameter analysis indicated that: the promotion of chloride ion transport by water pressure was limited, but the influence on the rust expansion failure of the concrete lining was relatively obvious. The enhancing the strength of concrete can prolong the time of cracking, but when the strength reaches a certain threshold, as the fracture energy of concrete no longer increases, the time of cracking will tend to stabilize.