Abstract: 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 um,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 320256 and the pixel pitch of 30 um.