An effective method for analytical calculation of polarization characteristics of radiation multi-scattered by turbid medium is considered. The efficiency of the method is in the assumption that the complete solution of vector radiative transfer equation (VRTE) is the superposition of the anisotropic and smooth parts, computed separately. The vector small-angle modification of the spherical harmonics method (SGM) is used to evaluate the anisotropic part, containing all singularities of the solution; and the matrix discrete ordinates method is used to obtain the smooth one, adding SGM to complete VRTE solution. The process of polarized radiation transfer is considered in a horizontally infinite layer of an arbitrary optical depth, irradiated by a plane mono-directed radiation source. Calculation examples are given for natural nonpolarized radiation. However, advantages of the suggested method carry over an arbitrary (including three-dimensional) geometry of scattering medium, arbitrary form of source, and radiation polarization state.