AbstractX‐ray measurements (specular and off‐specular X‐ray reflectivity, in‐plane and plane‐normal diffraction and truncation rod measurement) were carried out to characterize the epitaxial magnetic multilayers of yttrium iron garnet/gadolinium gallium garnet(GGG) on GGG substrate grown by the laser ablation deposition method. The perfection of the multilayer epitaxy can be better revealed in the observation of the 2nd harmonics of superlattice peaks in the reflectivity measurement, the forbidden diffraction peaks and the truncation rod measurement.