We propose a method to describe accurately Mössbauer spectra recorded on nanocrystalline FINEMET-type alloys by means of two independent components. The validity of the fitting procedure is controlled by comparing hyperfine characteristics of spectra recorded under different experimental configurations. In addition, the reliability of the fitting model is discussed from spectra obtained on nanocrystalline alloys resulting from different annealing treatments, i.e., with different crystalline contents. Such a method allows us to estimate more accurately the crystalline fraction and to refine the values of hyperfine parameters, both their annealing temperature and time dependencies, the hyperfine field distribution characteristic of the intergranular component and the magnetic texture. Finally, their changes versus crystalline fraction provide relevant information to describe the nanocrystallization process occurring during the transformation from the amorphous into the nanocrystalline state in the case of FINEMET alloys.