Abstract: In order to study effect of atmospheric channel on the beam quality under special circumstances,an indoor experiment system was built to simulate the situation dual wavelength laser passing in the same channel.Experiments were carried out under the conditions of different concentration fume and dust.It was found that attenuation coefficient linearly changed with air vapor density,the attenuation coefficient changed smaller with longer wavelength,and that it tend to the same when fume density reached to some extent.On the basis of measurement data,transmittance changed with dust concentration exponentially,which coincided with Beer-Lambert law.Experimental test data results accorded with atmospheric scattering theory.The results have reference value to study about atmospheric influence on light.