Using finite element method, nonlinear stress, such as contact borderline and large deformation of C seal ring in high-pressure quickly opening blind plate, was analyzed. Through modeling and analyzing computing with ANSYS, contact deformation, contact stress and its distribution characteristics were obtained. And also, distribution law of contact pressure between seal ring and barrel of blind plate, and relationship between distribution and medium were gained. Furthermore, seal ability of C compound structure’s servo seal ring was effectively analyzed.