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In this letter a Monte Carlo (MC) algorithm is used to simulate the propagation of polarized light in double-layer turbid media and the 2-dimentional backscattered Stokes vectors and Mueller matrices are obtained. Relationships between backscattered Mueller matrix and optical properties, such as scattering, absorption and layered structure, are discussed in detail. Integrating the 2-dimentional Mueller matrix elements along radial and azimuthal directions, we obtain a reverse trend with respect to the optical parameters for upper and lower layers, which suggests possibilities for discriminating subtle optical properties in a double-layer structure using backscattered polarization patterns such as Mueller matrix.The researches on light propagation in turbid media have attracted significant interest because of its practical applications, especially in noninvasive optical diagnosis and imaging through biological tissues [1][2][3][4] . Several recent studies have demonstrated that the relevant information of turbid media can be derived by analyzing the backscattered polarization patterns of the sample [5][6][7][8][9][10][11][12][13][14] . All these studies are aiming at analyzing sample's properties using polarization patterns. In this paper we extend the existing approaches and induce integration functions to discuss the influence of optical properties, such as absorption and scattering, on backscattered polarization patterns, and the results show that it is feasible to discriminate the optical parameters in doublelayer turbid media.Light transport behavior in turbid media can be well described by Boltzmann transport equation (BTE), but the analytical solution to the BTE is difficult to obtain in the strongly scattered bio-tissue applications. Monte Carlo (MC) method offers a versatile platform for solving such equations by numerical computation. In this letter the MC method is applied under following assumptions: elastic scattering, steady state, independent scattering events, and no coherent effects. Changes in polarization, when photons are scattered, are conducted in the far-field approximation. The polarized patterns of the media are calculated by tracing a large number of phonons and averaging their corresponding Stokes vectors and Mueller matrix. The standard Wang-Jacques MC model and polarized MC computation method have been discussed in detail [15][16][17][18] , and the differences between the present study and those reports are as follows.Refractive index mismatch is considered when a phonon walks across the boundary. The reflective and refractive instants are incorporated by reflective matrix M r and refractive-matrix M t , which are derived from Fresnel's law and Snell's law respectively: