The effect of replacement Si by P on the soft magnetic and structural properties of nanocrystalline Fe-Si-B-P-Cu alloys has been investigated. The nanocrystalline Fe 83.3Si XB 8P 8-XCu 0.7 (X = 0, 2, 4, 6) alloy ribbons consist of precipitated α-Fe phase and residual amorphous phase, and initial permeability of these alloy ribbons are enhanced with decreasing Si content. In particular, the nanocrystalline Fe 83.3B 8P 8Cu 0.7 (X = 0) alloy has both low core loss of 1.4 W/kg at 1.0 T - 50 Hz and high saturation magnetic flux density of 1.70 T. In addition, this alloy exhibits the most favorable nanocrystalline structure containing the homogeneously precipitated α-Fe grains with 14 nm in mean diameter. Therefore, it can be concluded that the soft magnetic properties and nanostructure of Fe-Si-B-P-Cu alloys are strongly affected by Si and P content. The Fe 83.3B 8P 8Cu 0.7 alloy with low core loss and high saturation magnetic flux density compared with a Fe amorphous alloy is suitable for a magnetic core material in electronic devices such as transformers, inductors and motors.