[en] Nanocrystalline transformation from amorphous matrix in Fe₆₆Cr₈Cu₁Nb₃Si₁₃B₉ alloys is investigated by synchrotron radiation extended X-ray absorption fine structure (EXAFS) and analyzed by the cumulant method. This method allows a refined study of the parameters that can describe the structure during the nanocrystallization due to the determination of nearest-neighbour interatomic distance and coordination number for Fe and Fe₃Si in these alloys. The formation of nanocrystals can be elucidated in two stages of nanocrystallization process. The first stage reveals the precipitation of BCC Fe in the core of grains and the second stage shows evidence for the formation of Fe(Si) around the iron nanocrystals. This suggests that, Si atoms diffused out from the core of grain leaving the iron in the first stage and some of the Si atoms bring together with Fe in the surrounding to form Fe₃Si in the second stage of crystallization. Thus, the cumulant analysis of EXAFS is able to provide detailed knowledge on the nanocrystallization processes