Taking the piston seal structure of pressure compensator of deep-sea equipment in the deep and ultra-high pressure environment of the whole sea as the research object, a nonlinear two-dimensional axisymmetric model of the seal structure was established based on the ANSYS WorkBench finite element simulation software. According to the selection and comparison of different materials in the deep sea environment, fluororubber and PTFE were selected as the seal materials, and the influence of different factors such as pre compression ratio, different friction coefficient, Hardness, and seal direction on the seal performance was analyzed, Finally, a sealing performance test was conducted on the Step sealing ring. The results indicate that for the Step seal, the higher the pre compression rate, the greater the contact pressure, and the contact pressure on the sealing surface gradually decreases along the contact surface. It is recommended to choose a pre compression rate of around 20% or higher as much as possible. The Von mises stress of Münster seal under ultra-high pressure environment is concentrated at the stepped slip ring and groove extrusion and the stepped angle of the stepped slip ring. With the increase of friction coefficient and Hardness of O-ring, the contact pressure is higher. The final test results show that Step seal can meet the requirements of piston sealing performance in deep sea ultra-high pressure environment.