Molibdenum-silicon multilayer structure as a soft x-ray mirror fabricated using a magnetron sputtering system has been studied through x-ray diffraction (XRD) of Cu K(alpha ) (1.54 angstrom) radiation. The angular positions, the relative intensities, the widths of Bragg primary and secondary peaks in XRD pattern are sensitive to structural parameters such as unit thickness (bi-layer thickness), thickness ratio of composite materials, diffusion lengths, and roughness. Effects of each structural parameter on XRD pattern have been investigated. The results show that the angular positions of Bragg primary peaks are sensitive to the bi-layer thickness, the pattern of secondary peaks is sensitive to the thickness ratio. It is also found that the major effect of interfacial diffusion is the reduction of the intensities of high-order Bragg primary peaks, and roughness is responsible for the broadening of the widths of Bragg primary peaks and the increase of the intensities of Bragg secondary maxima. Using the above results, we have analyzed experimental XRD data to draw the structural parameters of Molibdenum-silicon multilayer structure.