Epitaxial PbSe-EuS multilayer subjected to diffusion annealing was examined by low-angle X-ray diffraction and Bragg X-ray diffraction. Multilayer profile change in the course of diffusion intermixing was determined by simulation of X-ray diffraction on the model multilayer profile and comparison of calculated patterns with experimental ones. The systematic shift of the average Bragg peak found at diffusion shows the presence of Kirkendall effect in the specimen. Matano procedure was applied to calculate the partial diffusion coefficients of the multilayer components.