Abstract: The high-temperature soft magnetic properties were investigated for nanocrystalline（Fe_0.5-Co_0.5）_73.5Cu₁Mo₃Si_13.5B₉ alloy annealed at 460-580℃.The results show that by substituting Co for Fepartially in Fe_73.5Cu₁Mo₃Si_13.5B₉ alloy,a dual-phase nanocrystalline microstructure composed ofα-Fe-Co（Si） and residual amorphous phase is formed and the high-temperature soft magnetic properties are improved significantly.Compared with nanocrystalline Fe_73.5Cu₁Mo₃Si_13.5B₉ softmagnetic alloy,the Curie temperature that represents magnetic stabilization for（Fe_0.5Co_0.5）_73.5Cu₁Mo₃Si_13.5B₉ alloy is enhanced remarkably.Although the initial permeability μ_i of the new alloy at room temperature is decreased some what than that of Fe_73.5Cu₁Mo₃Si_13.5B₉ alloy,however,the μ_i at high-temperature is much more stable up to 450℃.Therefore a potential application as high temperature soft magnetic materials for this alloy is expected.The mechanism that the high-temperature soft magnetic properties can be improved by partially replacing Fe with Co in Fe_73.5Cu₁Mo₃Si_13.5B₉ alloy was also discussed.