We have carried out an experimental study based upon the ferromagnetic resonance (FMR) on the anisotropy of alloy ribbons of (Fe1-xCox)84Zr3.5Nb3.5B8Cu1(x=0.0, 0.2, 0.4, 0.6, 0.8). The easy axes of the samples are in the lateral direction of the ribbons, While the single-axis anisotropy c onstant K′ of the samples having the same width decreases as the amount of Co i ncreases. The value of K′ lies between 4.67×10-5J/m4(x=0 .0) and 2.54× 10-5J/m4(x=0.8). Since the imaginary part χ″ of the alte rnating curren t magnetic susceptibility changes nonlinearly with the magnetic field H, there is a low field (0—12　mT) non_resonance signal having a comparable strength wit h that of the ferromagnetic resonance signal. It is found through the study on t he magnetic process of the alloy ribbon of Fe84Zr3.5Nb3.5B8C u1 that dχ″/dH=0 in the regions of the reversible (0—12　mT)　and saturated (9.0 mT—12 mT) magnetization that χ″(H) is related to the n_th power of H, i .e., Hn(n≥3) when the domain wall motion is nonreversible; and χ″ is relate d to H2 during the domain rotation (Rayleigh region, dχ″dH is a con stant). S pecifically, it is found that the χ″(H) proportional to H2 and tha t proportional to Hn(n≥3) appear alternatively in three sections, correspon ding to the disappearance of different domains.