Process of nanostructure formation in amorphous alloys Fe—P–Si–Mn—V and Fe—P– Si–Mn—V—C is studied. It is shown that nanocrystalline structures can be obtained under thermal effect on amorphous iron-phosphorous alloys. Annealing of these alloys at temperature below crystallisation temperature leads to formation of nanocrystalline structures. Thus occurs to hardening them for 1,8–2,5 times in comparison with an amorphous state. Mossbauer researches of alloys in amorphous and annealed state have shown that alloys can be alloyed by all elements contained in electrothermal ferrophosphorus and they can possess soft magnetic properties. The conclusion is drawn that amorphous and nanocrystalline Fe—P–Si–Mn—V—C alloys in absence or at presence of small quantity of paramagnetic phases will possess optimum magnetic properties.