Abstract: This study focuses on special-shaped inflatable membrane structures utilized in underwater waterproof systems, exploring the impact of diverse membrane materials and bending stiffness on their wrinkling deformation. Initially, theoretical analysis was carried out to deduce equilibrium equations taking into account both material elastic deformation and bending stiffness, thus uncovering the deformation response control mechanism of special-shaped inflatable membranes. Subsequently, a coupled numerical simulation method founded on the CEL method and fluid cavity method was developed to attain simulation of the entire operational process of inflatable membranes under intricate underwater conditions. Finally, by leveraging this validated coupled numerical model, comparative analyses of wrinkling deformation were conducted across different membrane types. Simultaneously, the impact of considering or disregarding bending stiffness on the overall structural deformation was quantitatively evaluated. The results suggest that wrinkling deformation is fundamentally a local instability behavior of spatial membrane structures. Nevertheless, for underwater waterproof special-shaped inflatable membranes, local wrinkling does not necessarily imply structural failure. Instead, the generation of wrinkling strain can optimize the overall stress distribution and deformation compatibility. The incorporation of bending stiffness results in a stable deviation of less than 12% in the maximum strain, with a negligible effect on the overall deformation of the special-shaped inflatable membrane. Based on these findings, within the acceptable engineering accuracy, the influence of bending stiffness can be neglected in future numerical analyses of similar structures, offering theoretical support for the efficient simulation and engineering design of underwater special-shaped inflatable membranes.