Abstract: In order to meet the need of safe and stable operation of deep-sea equipment under the special working conditions of deep-sea high pressure, with the combined seal structure under deep-sea high-pressure environment as the object, the axial symmetry finite element model of the combined seal structure is established by the ABAQUS finite element analysis software, and the influence of the material hardness of different O-ring seals on the performance of the combined seal structure is analyzed. The results show that the maximum Von Mises stress of the O-ring decreases with the increase of the material hardness, but the maximum contact pressure of each sealing lip of the seal ring and the slip ring gradually increases as the material hardness increases. When the O-ring material has a low hardness, the O-ring will be squeezed into the gap between the slip ring and the groove, causing a “sharp angle” phenomenon, which in turn causes the seal structure to fail. The research results provide theoretical basis and technical support for the optimization of combined seal structural materials and the optimal design of seal structures in deep-sea high-pressure environment.