The Mossbauer spectra were measured at room temperature for the nanocrystalline Fe73.5Cu1Mo3Si13.5B9 alloys at the as-cast state and the anneals at various temperatures. The results of measurements demonstrate the co-existence of the α-Fe(Si) nanocrystalline phase and interficial amorphous phase in the crystallized alloys. The variations of the hyperfine field and relative areas of these phases with the annealing temperature are attributed to the annealing-induced diffusion of Cu,Mo, B and their redistributions in these phases.30 percent of iron contained in the amorphous phase was found and this state of affairs corresponds to the best magnetic properties. The two-phase, disordered anisotropy model makes clear, that a certain amount of amorphous phase was essential to the excellent soft magnetic properties of nanocrystalline alloys. The deterioration of the properties is due to the existence of Fe2B phase .