Abstract: As an important part of the air-to-air missile, IR optical system will experience various complex dynamical situations. A complete analysis to the deformation, stress, and resonance of IR optical system was made with the finite element method to validate whether the optical system meets the image quality and mechanical stiff requirements, and the distinct deformation area was determined. The key structures of the optical system were analyzed in detail, and the approach to optimize the structure of the system was proposed.