According to structural feature and seal requirement for large scale cutting tube machine, the non-standard rubber lip seal ring was self-designed. The nonlinear finite element contact analysis was utilized to model, calculate and optimize the structure of the lip seal ring, so as to improve the seal performance of the lip-shaped seal ring, and to determine the criterion for failure of seal performance of the lip seal ring, therefore to lay a foundation for the optimal design and performance research of the lip seal ring. According to the actual working pressure for the cutting tube machine, the stress and deformation for the lip seal ring were simulated. It has been testified by the practical use that the finite element analysis is correct. The method to optimal design of the seal structure with finite element analysis is feasible.