Currently, the development of hypersonic vehicles and propulsion systems has brought great challenges to the structural design and material properties of experimental facilities such as wind tunnels. The flexible plate nozzle, as a core component of wind tunnel equipment, achieves continuous variable Mach number by changing the shape of the nozzle wall. During the molding process of the flexible plate nozzle, the adjustable and fixed contraction segments are moving in the dynamic movement, while the flexible wall components and side walls are also in a relatively sliding state. Gas can leak out of these structures, which adversely affects the efficient construction of the test flow field. Therefore, more stringent challenges are posed to its sealing structure. These challenges include: extremely high temperature environments, ultra-high aerodynamic loads, high pressure fluctuations, minimal leakage, etc. To meet these challenges, the corresponding requirements for high-temperature dynamic seals become extremely stringent, requiring capabilities such as high heat resistance, strong sealing, high-temperature resilience, and compensatory ability. Therefore, this paper designs a sealing structure that can effectively seal the gap in such harsh aerothermal environments and adapt to large gap variations within limited space. Based on the designed dynamic sealing structure, a calculation method is provided.