Nanomodification and amorphization are vital for improving the hydrogenation properties of magnesium (Mg)-based alloys. However, comparisons of their positive effects have been rarely presented because their usual fabrication process of annealing is hard to control. In this study, after tuning the composition fluctuation range, self-assembled well-ordered multilayer Mg0.7Gd0.3 films with an excessive amount of nanosized crystals were fabricated by deviating substrates to the edge of the sample stage, while relatively low crystallinity was gained at the center of the sample stage with a small composition fluctuation. It was demonstrated that the hydrogen diffusion rate in the sample deposited at the center with excessive amorphous regions was higher than that of the film fabricated at the edge with excessive nanocrystals regions. Besides, optical conversion ranges were monitored before and after the hydrogen absorption process. Films with large composition fluctuation possessed a high optical reflectance conversion range because the interference effects occurring inside improved their initial reflectance. However, films with small composition fluctuation inside gained a large transmittance conversion range due to their small nanostructured region.