Abstract: The magnetic properties of 520℃ isothermally annealed nanostructural soft magnetic alloy Fe_73.5Cu_1.0Mo_3.0Si_13.5B_9.0 for different annealing times are investigated. The high soft magnetic properties have been obtained and the initial peameability μ_i reaches 5 × 10⁴ when the annealing time is 40min. The factors influencing on magnetic properties are discussed.