Polarized neutron reflectometry was used to study Dy/Gd superlattices with different ratios of Dy and Gd layer thicknesses: 1 : 1, 2 : 1, 3 : 1. It has been experimentally shown that the formation of helical magnetic ordering in Dy layers with a period incommensurate with the period of the superlattice appears as a magnetic superlattice reflection, which is forbidden for structural reasons at a ratio of the thicknesses of the Dy and Gd layers 1 : 1. Otherwise, the formation of helical magnetic ordering has little effect on the shape of the neutron reflectometry curves. Thus, the optimization of the structure of rare-earth superlattices for the neutron reflectometry experiment makes it possible to detect helical magnetic ordering in superlattices with a period incommensurate with the structural superlattice ordering.