Аннотация:The method of investigation applied to spatial spin-modulated structure (SSMS) of the cycloid type in multiferroics based on the Mössbauer spectroscopy is discussed. It is shown by the example of bismuth ferrite BiFeO3 that the usage of Mössbauer spectroscopy can define the anharmonicity parameter of the cycloid type SSMS with preciseness not less than obtained by the NMR-method characterized by much better resolution. The Mössbauer spectroscopy method, sensitive to hyperfine electric quadrupole interaction of nuclei in excited state, makes it possible to obtain additional data on SSMS peculiarities. The anharmonicity parameter for BiFeO3 has been derived at various temperatures ranging from 4.85 K to 600 K.