Abstract: To investigate the influence of external water pressure conditions, chloride ion concentration, erosion duration, and additional loads on the development pattern of chloride-induced corrosion damage in lining segments, a numerical model for chloride-induced corrosion damage of segments in shield tunnels is developed using the COMSOL Multiphysics finite element platform, based on the Jiangyin - Jingjiang Yangtze River Tunnel project. The structural mechanics module, porous media dilute substance transport module, Richards equation module, and three - dimensional current distribution module were selected to construct a multi - field coupling model. The damage evolution pattern of concrete under the combined action of eccentric loads, high water pressure, chloride ion erosion, and steel bar corrosion expansion is systematically simulated. The corrosion expansion mechanism of the tunnel lining structure in complex environments is elucidated, and engineering protection recommendations are put forward. The results indicate that under the combined action of high water pressure and eccentric loads, the lining segments will exhibit significant steel bar corrosion and corrosion expansion phenomena, resulting in a structural damage area ratio exceeding 50%. The damage area expands in a strip along the direction of the steel bars, and the degree of damage increases non - linearly with the erosion duration, which may ultimately lead to the overall deterioration of the structure.