A Monte Carlo simulation model for the diffuse backscattering of the polarized l ight from the poly_disperse highly dense media is developed and the effective fr ee pathlength distribution function of the poly_disperse system is given. Simula tion is conducted for the mono_disperse polystyrene suspensions with particle si zes of radii 50 and 550nm, and poly_disperse suspensions containing the above tw o particles with the volume fraction ratios of 4:1, 1:1 and 1:4 The relation b etween the spatial intensity variations of the light diffuse backscattering patt ern and the volume fraction ratio of the poly_disperse suspensions is analyzed q ualitatively.