Artificial sprays can be used in the fire safety and infrared stealth because that they can strongly attenuate the heat radiation through the scattering and absorbing effect. A model is established to calculate infrared radiation attenuated in the spray by coupling the radiation transfer equation and energy conservation equation. Taken the sprays as an absorbing, emitting, anisotropic scattering non-gray medium, the medium radiation, multiple scattering of the sprays, target radiation flux, and environment are taken into account. The radiative coefficients are calculated through Mie law and narrow bands approximation. The hemispherical spectral transmissivity is calculated with this model. By comparing with the Lambert-Beer's law, it was found that medium radiation, multiple scattering, and target radiation flux can weaken the spray shielding efficiency.