Abstract: The effect of the Si content on magnetic properties for nanocrystalline Fe_87-xCu₁Nb₃Si_xB₉ alloys annealed in different methods has been investigated. It was found that the magnetic properties of Fe_87-xCu₁Nb₃Si_xB₉ alloys annealed in normal methods were obviously improved with the increasing Si content. Annealing under a magnetic field can induce an uniaxial anisotropy and the magnetic annealing feature was increased with the increasing of Si content. According to the results calculated from traversal magnetic annealing,the magnitude of induced magnetic anisotropy Ku was induced from 26.7J/m³ （Si=9.5at%） to 14.1J/m³ （Si=13.5at%）. Analysis of the experimental data suggests that the excellent soft properties for Fe_87-xCu₁Nb₃Si_xB₉ alloys with more Si content after normal or magnetic annealing are attributed to a smaller magnetic crystalline anisotropy K₁ of precipitated α-Fe（Si） grains,which results in much lower effective magnetic anisotropy ＜K＞.