Abstract: The inflatable valve gasket of attitude and rail control engine is prone to creep under long time high-pressure working condition. It leads to valve leak because of gasket seal failure, which seriously affects the safety and reliability of attitude and rail control engine. To solve the sealing problem caused by the creep of fluorinated ethylene propylene gasket, tests on mechanical behavior and compression creep were carried out. Creep coefficients A, m, n of FEP material were obtained by Origin curve fitting. The age-hardening creep model of sealing was established by analyzing the effects of time, working pressure, structure parameters and materials on the creep and sealing performance of FEP gasket using finite element method. The simulation of the static compression creep test process of FEP material was verified by experiments, and the error rate between simulation and test was less than 10%. The service time of FEP gasket was 571.67 hours and the maximum working pressure was 54.32 MPa. Reducing the fillet radius and increasing the height of the bump can lessen the equivalent Mises stress to reduce the chance of cracks, but also lessen the contact stress.