The calculation model of airframe’s infrared radiation was established. Based on the factors of aerodynamic heat convection,environmental radiation,internal heat source’s radiation and heat conduction on air-craft’s skin,the thermal network equation was established,a wall heat flux function was derived as a flexible thermal boundary condition,and airframe’s temperature distribution was obtained by numerical calculation of airframe’s external flow field. Then the total infrared radiation intensity of airframe with different gazing directions and different wavelength was calculated. The obstruction between skin cells is considered when the airframe’s total radiation on the line of sight is calculated. Finally,the effect of sun radiation,flight speed and flight altitude on airframe’s IR radiation is discussed.