In order to analyze and study the infrared radiation characteristics and radiation brightness distribution of transport aircraft, the infrared radiation luminance of airbus A320 aircraft in head-on flight state is measured by using medium wave of 3.7~4.8 μm and long wave infrared thermal imager of 7.7~10.3 μm. The infrared radiation is described by relative contrast. The results show that the main source of aircraft infrared radiation is skin radiation caused by aerodynamic heating. The brightness contrast of medium wave and long wave is 0.61 and 0.37 respectively, which is higher than that of skin of other parts of the fuselage. The brightness contrast of medium-wave and long-wave radiation of wing and tail is 0.04~0.05 and 0.02~0.10, respectively, which is the lowest part of the skin radiation of the aircraft. The brightness contrast of medium-wave radiation in the belly and nose of the aircraft is higher than that of long-wave radiation, with the contrast between 0.30~0.33 and 0.16~0.18, respectively. The research conclusion has certain reference value for target characteristic research, infrared reconnaissance and detection, infrared reconnaissance equipment development and detection.