Abstract: For strongly attenuating the heat radiation through scattering and absorbing effect, fine water sprays are used in military object infrared stealth. The 8-14 m infrared radiation attenuation model by water sprays was established, in which water sprays were treated as absorbing, emitting, and anisotropic scattering medium and non-grey properties were dealt with bands discretion method. The average optical parameters in the discrete spectral bands were got by Mie theory and the radiation transfer process was carried out with finite volume method. It is found that there would be some errors when the polydisperse sprays are treated as monodispersion. The errors resulting from Sauter radius is minimum, where as that from the linear average radius is maximum. The inner radiation and scatter of the sprays have biggest influence on the transmission, so it should be considered during calculations. For restraining the radiative transmission effectively, the measures of increasing the sprays concentration and decreasing the geometry average radiuses should be done.