In order to improve the precision of infrared systems in sand and dust storms, by using the multiple scattering theory of electromagnetic wave propagation in discrete random medium, the backscattering enhancement mechanism was analyzed for infrared wave propagating in sand and dust storms. The formula about the relation of the particle number per unit volume and atmosphere visibility was presented in sand and dust storms. From visible light to far infrared wave, the backscattering enhancement caused by multiple scattering in sand and dust storms was researched for different visibilities. The results show that the backscattering enhancement for different wavelength waves is different. The lower visibility in sand and dust storms, the stronger backscattering enhancement is. For different types of sand and dust storms, the particle size distribution is different. At a given visibility, the particle number per unit volume is larger, the backscattering enhancement are stronger. At a given particle number density, the number of the larger size particles is larger, the backscattering enhancement is stronger. Especially, the enhancement for the longer wavelength wave is more obvious. That is, the lower visibility, the larger number per unit volume, and the more the larger size particles, the backscattering and enhancement is stronger in sand and dust storms, and the effect on infrared systems is severer.