This article describes a novel configuration design for a re-imaging off-axis catadioptric space infrared optical system,and in order to satisfy the signal noise ratio requirements of the system,the stray light of the system is necessary to analyze and restrain. The optical system with a focal length of 1 200 mm,an entrance pupil diameter of 600 mm,an F-number of 2,a field of view of 3°× 0. 15°,a working wave band of 8 μm-10 μm,and the image quality of the optical system almost approach to diffraction limits in all field of view.Then the mathematical models of stray light are built,and the suppressive structure is established to eliminate the effect of stray light. Finally,TraceP ro is used to analyze and simulate stray light with and without the suppressive structure,and also get the results of the PST curves. The results indicate that appropriate optical system and suppressive structure can highly reduce the stray light of the space infrared optical system. This article describes a novel configuration design for a re-imaging off-axis catadioptric space infrared optical system, and in order to satisfy the signal noise ratio requirements of the system, the stray light of the system is necessary to analyze and restrain. The optical system with a focal length of 1 200 mm, an entrance pupil diameter of 600 mm, an F-number of 2, a field of view of 3 ° × 0.15 °, a working wave band of 8 μm-10 μm, and the image quality of the optical system almost approach to diffraction limits in all field of view. Then the mathematical models of stray light are built, and the suppressive structure is established to eliminate the effect of stray light. Finally, TraceP ro is used to analyze and simulate stray light with and without the suppressive structure, and also get the results of the suppressive structure, and also get the results of the PST curves.