Abstract: In the ranges of f=10-3×10³Hz and B_m =0.1-1.0T, the dependence of total core loss per cycle P/f on frequency f was investigated for nanocrystalline Fe₇₃Cu₁Nb₂V_1.5Si_13.5B₉ alloy with high B_r. The behavior of P/f vs f exhibits clearly non-linearity.The non-linearity is obvious in the range below about 200Hz.The non-linear behavior can considerably well be described in terms of the behavior of the simultaneously active"Magnetic Object"（MO）in the statistical theory of power loss. In the lower frequency segment, the number n of the active MOs is near-linearly associated with the dynamic excess field H_exc, whereas the dependence of n on H_exc clearly exhibits non-linearity in the wider and higher frequency segment.