Amorphous Fe78Si9B13 alloys were treated by low frequency pulse magnetic field. The temperature rise in the course of the treatment of pulsed magnetic field was measured by a non-contact infrared thermometer. The microstructure changes of amorphous specimens after treatment were observed by M?ssbauer spectroscopy and TEM. The results show that the nanocrystallization of amorphous specimens can occur at low temperature. When the temperature rise is under 7 ℃, the precipitation content and the grain size of the nanocrystalline phase α-Fe(Si) with bcc crystal structure are about 2.18%~9.43% and 10 nm, Respectively. Compared with the original amorphous alloy, the double- phase (amorphous nanocrystaline) nanocrystalline alloy has obvious high mean hyperfine magnetic field