The Fe–Si–B–P–Cu nanocrystalline alloys exhibit high saturation magnetic flux density (B s ) as well as good soft magnetic properties such as low coercivity, high effective permeability and low magnetostriction after nanocrystallization. In this paper, the Fe 85 Si 2 B 8 P 4 Cu 1 alloy has been newly developed. On the viewpoint of magnetic softness, the Fe 85 Si 2 B 8 P 4 Cu 1 nanocrystalline alloy reveals low core loss (W) at a commercially frequency of 50Hz in the maximum induction (B m ) range of up to 1.75T, and the W in the B m range of less than 1.8T is smaller than that of the highest-graded oriented Si-steel due to high magnetic flux density at 800A/m (B 800 ) of above 1.8T and excellent magnetic softness originated from much higher Fe content and uniform nanocrystalline structure with small magnetostriction. The electrical resistivity (ρ) is relative higher than Si-steels. Thus the Fe–Si–B–P–Cu alloys are attractive for applying to magnetic parts such as motors, transducers, choke-coils and so-forth.