Elastomeric O-ring seals are widely used in static and dynamic applications due to their excellent sealing capacity, and availability in various costs and sizes. One of the critical applications of O-ring seals is solid rocket motor joint seal. In this, the operating hot gas must be sealed during the combustion time. In this study, we analyzed the behavior of O-ring compressed and highly pressurized by using the finite element method. The numerical analysis technique was verified through the comparison of analytical model and FE results. By using the verified FE method, the contact stress profiles at the sealing surfaces were investigated. It was found out that the contact stress profiles and deformation behaviors of the Oring are affected by friction coefficient, extrusion gap and stress relaxation considerably.