The roles of Nb played in crystallization procedure of nano-crystal Nd2Fe14B permanent magnet were investigated by XRD, TEM and 3DAP. The results revealed that the addition of Nb improved the glass formation ability of the alloys and the thermal stability of the as-spun amorphous ribbons, as well as improving the optimum crystallization temperature. Nb atoms, together with more B atoms and some Fe atoms, had some enrichment in the as-spun ribbons, but few or no Nd atoms were found at these Nb-enriched regions. Nb-enriched phase hindered the growth of Nd2Fe14B grains, refined the microstructure and improved the magnetic properties