Abstract: The effect of Si content on the structure and properties of FeSiBPCu alloy was studied. A method of replacing B element with Si element was proposed to analyze the effect of element content on the structure and properties of FeSiBPCu alloy. The effects of Si content variation on the amorphous formation ability, thermal stability and soft magnetic properties of FeSiBPCu alloys were analyzed by X-ray diffraction, differential scanning calorimetry, vibrating sample magnetometer and scanning electron microscopy. The experimental results show that the five different components of the samples show amorphous structure, and the addition of Si is beneficial to improve the amorphous forming ability of the alloy. With the increase of Si content, the initial temperature of the first crystallization moves to the low temperature zone, and the initial temperature of the second crystallization moves to the high temperature zone, which obviously expands the temperature range between the two crystallization times and increases the annealing range. With the addition of Si element, the saturation magnetization of the quenched strip is basically unchanged, and the maximum value is 149 emu·g⁻¹. The quenched Fe₈₀Si₆B₁₀P₃Cu₁ amorphous thin band with good soft magnetic properties was selected for crystallization annealing treatment at different temperatures for 10 min, and nanocrystals began to precipitate when the temperature exceeded 730 K. With the increase of annealing temperature, the precipitation density of nanocrystals increased and the grain size increased. The annealed amorphous/nanocrystalline alloy has good soft magnetic properties. It shows a high saturation magnetization (181 emu·g⁻¹). The addition of appropriate amount of Si element is beneficial to improve the amorphous formation ability and soft magnetic properties of FeSiBPCu alloy.