<p>Dual-nano-phase alloys with an ultrafine crystal-glass imbedding nanostructure exhibit exceptional high structural and functional performances, yet they generally suffer from the dimension limit and the harsh manufacturing process, especially for the one with a simple nanocrystalline phase comprised of the principal component. Here, an innovative composition design strategy was developed to unprecedentedly combine the high glass-forming and α-Fe nanocrystallizing abilities in Fe-based alloys, via kinetically slowing the devitrification process and thermodynamically facilitating the α-Fe nanocrystallization. The newly developed (Fe₇₁Nb₆)_<i>x</i>/77B_100-<i>x</i> alloys exhibit a high glass-forming ability (critical dimension of 1&#xa0;mm) for fast solidification productions of glassy precursors and a large temperature interval for the nanoprecipitation, meeting the requirements of multiple industrialization techniques. Moreover, the alloys possess attractive soft magnetic properties in multi-states, overcoming the common problems of the grain coarsening and property fluctuation. These are of paramount importance for the widespread applications of the emerging materials, and can mechanistically reveal the intrinsic connection between the glass formation and nanocrystallization.</p> Graphical abstract <p></p>