In order to reduce the contribution of the last-stage turbine of the infrared radiation in backward of the exhaust system, the full shielding guide vane(FSGV) is designed to achieve full shielding of the low-pressure turbine. Numerical simulation methods are used to study fluid flow heat transfer and infrared signature of three exhaust system (including baseline axisymmetric exhaust system,2D exhaust system and 2D exhaust system with FSGV) models combined with aircraft rear body, revealing the general rule of infrared radiation characteristics in the 3-5 μm band in backward of the three different combined models; the results show that compared with the baseline axisymmetric exhaust system model combined with aircraft rear body, whether it is a 2D exhaust system model combined with aircraft rear body or 2D exhaust system model with FASG model combined with aircraft rear body, the infrared radiation intensity has been reduced, and the drop rates are 22.1% and 46.9% respectively at a detection angle of 0°. If the cooling technology is adopted for the FSGV, as long as cooling efficiency reaches 0.282 and 0.482, compared to uncooled state of the exhaust system, the infrared radiation in backward of the exhaust system can be reduced by 20.4% and 35.45%.