Because the surrounding rock mass of a subsea tunnel or an offshore water tunnel chronically resides in the groundwater environment, its stability is significantly influenced by seepage field, which can in turn induce stress variation and even damage in the rock mass. Conversely, the stress variation and rock damage can exert influence on the seepage field. In this study, inversion analysis is carried out to determine the material parameters for the coupling model. A computer program is developed using C++ language to describe the elastoplastic stress-seepage-damage coupling of the rock mass, and the intelligent back analysis is performed to examine the stability of the surrounding rock along the Dalian Maritime University subway test line under construction. The parameter inversion is performed based on the displacement data from field monitoring, and in calculation, the indirect iteration coupling method of stress field and seepage field is used. The stress distribution and seepage field of the supporting structure are analyzed using the inversion damage parameters of the surrounding rock. The results show that the mechanical parameters of the surrounding rock obtained from the displacement back analysis can be used in the numerical analysis of the surrounding rock of similar geological conditions. Based on this, the deformation of surrounding rock can be determined, and the stability of surrounding rock can be evaluated. It is also shown that the groundwater seepage has influence on the deformation of surrounding rock of an offshore tunnel, which can induce increase in the stress and displacement of the surrounding rock. The results can provide some guideline for the tunnel waterproof design and construction.