The flow field model of an aero-engine exhaust system including its inner and outer space is established and its temperature,pressure and consistency distribution are calculated by solving the Navier-Stokes equations.The absorption and emissivity of the water vapor,the carbon dioxide and the carbon monoxide must be considered，then the infrared radiation characteristic of the aero-engine exhaust system are calculated using integration method of the radiative transfer equation(RTE).The results indicate that the intensity distribution shape of Infrared radiation is no more “pear-like”,but “super ellipse-like”.