  The AFMR spectra of the NdFe$_3$(BO$_3$)$_4$ crystal are measured in a wide
range of frequencies and temperatures. It is found that by the type of magnetic
anisotropy the compound is an "easy-plane" antiferromagnet with a weak
anisotropy in the basal plane. The effective magnetic parameters are
determined: anisotropy fields $H_{a1}$=1.14 kOe and $H_{a2}$=60 kOe and
magnetic excitation gaps $\Delta\nu_1$=101.9 GHz and $\Delta \nu_2$=23.8 GHz.
It is shown that commensurate-incommensurate phase transition causes a shift in
resonance field and a considerable change in absorption line width.
  At temperatures below 4.2 K nonlinear regimes of AFMR excitation at low
microwave power levels are observed.
