The　paper　presents　a　laser　irradiation　method　for　rapidly　fabricating　Fe-based　nanocrystalline　alloys　using　Yb-doped　fiber　laser　with　a　wavelength　of　1070nm　by　overlapping　irradiation　of　the　heated　areas.　The　samples　are　annular　cores　rolled　with　20　mu　m-thick　and　3.2mm-wide　belts　of　amorphous　alloy　Fe73.5Cu1Nb3Si13.5B9,　which　have　internal　diameter　of　14　mm　and　external　diameter　of　20　mm.　Every　side　of　the　samples　is　irradiated　for　15　min　by　fiber　laser.　X-ray　diffraction　and　transmission　electron　microscopy　(TEM)　are　used　for　microstructure　analysis　and　observation.　The　samples　irradiated　by　a　defocus　beam　with　a　diameter　of　7.1mm　through　a　lens　have　better　soft　magnetic　properties　than　directly　by　an　original　collimating　beam　with　a　diameter　of　6.7mm.　The　dimension　of　homogeneous　ultrafine　grains　is　about　10nm　with　a　bcc　alpha-Fe　(Si),　which　is　the　foundation　of　the　excellent　soft　magnetic　property.　Uniform　laser　irradiation　and　the　appropriate　laser　power　are　necessary　for　optimum　microstructure　and　soft　magnetic　properties.