We have developed the general computer code for the calculations of reflectivity with polarization analysis from an arbitrary anisotropic multilayer, which allows us to test different approaches for the Bragg reflectivity spectrum treatment. We have proved the validity of the usage of the Bragg peak position for the determination of the energy dependence of the diagonal component of resonant susceptibility tensor, but revealed the essential discrepancy of this procedure for the off-diagonal term determination. The explanation lies in the polarization mixture by multiple reflections at large glancing angles. By the model calculations we have shown that in L-MOKE geometry the observed difference of the integrated Bragg peak reflectivity for the (+) and (-) field direction is predominantly caused by the magnetization of the central part of resonant layer at the first-order Bragg peak, but it is very sensitive to the interface magnetization at the second-order Bragg peak. (c) 2006 Elsevier B.V. All rights reserved.