The results of structure and magnetic investigations of Fe-Si system alloys synthesized from iron and silicon powder mixture by laser irradiation are presented in this paper. It is established that a many-phased structure is formed in the alloys, the phase concentration of which depends on the concentration of mixture components. The concentration maxima of the phases formed in the alloys correspond to the stoichiometric values of the initial mixture composition. The nanocrystalline structure distinguished for its hyperparamagnetic properties is formed in the synthesized alloys.