The inversion of low resolution infrared scanning equations for a cylindrically symmetrical combustion gas flow is investigated with CO2 (4.3?m) as emitting and absorbing medium. The Lorentz line random band model, exponential-tailed S-1 line trength distribution function and Curtis-Godson approximation are used to express the ransmissivity. An iterative solution of the radiation transfer equation for the temperature profile is established assuming a known absorbing gas concentration distribution. Numerical experiments show ihe iteration is simple and converges quickly with a high calculation accuracy. The temperature solution is stable 1o the intensity. Analyses show the influence of intensity error on temperature solution could be expected weaker, if the temperature is lower and the wavenumber used is largeAn approximate formular to calculate the absorbing gas concentration profile from the radiation transfer equation and the transroissivity equation Is derived. The inversion of the active infrared scanning equations is formed by combining the concentration formulae and the temperature iteration. Numerical experiments show the inversion is simple and accurate enough for the temperature measurement in engineering applications.