The temperature influence of each parameter in infrared detection imaging system was analyzed in the paper.Benefitting from infrared chalcogenide glasses less index temperature coefficient and catadioptric configuration excellent thermalization performance, a catadioptric MWIR detection thermalization imaging system by Code-v optical design software was presented.The working wavelength is 3.7-4.8 μm，effective focal length is 109.7 mm，field of view was 6.4°，F/＃ is 2.0 and cold shield efficiency was 100％.The design results indicate that the image quality in -40 ℃ and 60 ℃ have little changed, which compared with in 20 ℃.The system is compatible with staring focal plane array MWIR detector which has a format of 320×256 and the pixel pitch of 30 μm.