Based on X-ray dynamical theory, the double-crystal diffraction rocking curves for In-GaAs/InP single layer and InGaAs/AlInAs/InP superlattice were calculated for both perfect and rough interfaces. It is shown that the effect of roughness of multilayer interface on the zero-order diffraction peak was not obvious but severe on both the satellite peaks for superlattice and the interference fringes for single layer structure. With the increasing of the interface roughness, the intensities of interference fringes were reduced and disappeared. And for the satellite peaks, their intensities were reduced and the full width at half maximum broadened. Comparing the experimental result with the calculated one, we believe that there still exists an average roughness of about one monoatomic layer at the interface of high quality InGaAs/Al-InAs/InP lattice-match superlattice sample.