Characters of atmosphere and media play an important role in the transmittance of laser.To study the light propagation in homogeneous medium,an experiment system was set up.The dust density and particle kind can be set and adjusted in this indoor experiment system.Experiments on severeal different kinds of dust are described.Relationship between transmittance and the dust density is established.Results meet with the Lambert-Beer law and the atmospheric scattering theory.Attenuation parameter for different dust medium is different and can be given out by the experiments.The method is general and can be applied to study the laser transmittance in other dust media.