Abstract: A study establishing the infrared radiation contrast in wave band of infrared spectrum detection, based on the great difference of radiation characteristics in the narrow wave band about target and background, was proposed to accurately detect the infrared stealth targets whose infrared radiation characteristics were similar with that of background. The optimum wave band, through analyzing the relative contrast and absolute contrast of target and background and considering the influence of atmospheric conditions in the whole transmission procession, was determined 2.86-3.30 m and 4.17-4.55 m. The results show that the narrow wave band which was selected by infrared contrast could eliminate radiation of background well, highlighting the target radiation and enhancing the detectability of target.