Abstract: According to the typical structure of hybrid sandwich composite structures and the corresponding bearing force characteristics, this paper takes a certain submerged platform appendage structure as the research target. First, a model test scheme is designed, and the experimental study on compression load-bearing characteristics is carried out. Then, the Abaqus finite element model is established, whose validity is verified through comparative analysis with the experimental data. On this basis, further discussion about the deformation and strength characteristics of the main component of hybrid sandwich composite structures under static pressure in deep water environment is put forward. Finally, considering the design problem of the stress concentration area between steel frame and surface skin, the rationality and feasibility of the comprehensive evaluation of two types of T connection design are estimated. The results show that serious stress concentration of the skin and the core material could be avoided when the elastic modulus of the core material is between 4~8 GPa, which serves as valuable reference for future engineering design.