Abstract: Water leakage is more likely to occur at the segment joint of subsea shield tunnel and consequently it will accelerate the erosion and deterioration rate of the lining structure. A numerical model for the seepage erosion of segment joint of the subsea tunnel was established considering the penetration of sea water, erosion of chloride ion and water leakage. The migration law and effect of chloride ion erosion were analyzed under different external water pressures and volumes of water seepage. The results show that water leakage results in change of distribution pattern of seepage field in the adjacent area and increase of pore water pressure; water seepage aggravates the erosion of concrete at the inner side of segment, the larger the external water pressure, the more obvious the increase of deterioration, while the effect of water seepage volume can be ignored; the increase of external water pressure will increase the ion content on the surface of steel bar, reduce the inhomogeneity of ion distribution, and shorten the time to reach the critical ion concentration of steel bar, and the ion content of the steel bar surface increases with an in? crease of water seepage at the same time under small external water pressure; in the case of water seepage, the icon migration moves toward joint surface, the larger the water seepage, the more concentrating of moving track of icon.