The polarization-maintaining capacities of the backscattered linearly and circularly polarized lights in the scattering media composed of particles with different sizes are analyzed with the Monte Carlo simulation method. The comparative research of the micro-change in polarization states between the linearly and the circularly polarized lights in the process of every scattering event is performed by using the Rayleigh and Mie scattering theories. The results show that the polarization-maintaining capacity depends on the polarization state of incident lights and the size of the particles. As for the Rayleigh-scattering particles, the linearly polarized light has a stronger polarization-maintaining capacity. While as for the Mie-scattering particles, the circularly polarized light has a stronger polarization-maintaining capacity.