The undercooling degree above 0.3TI can be steady obtained by the technique of auto-seperating denucleation ofmolten glass for the (Ni0.53 Fe0.33 Co0.14)73B17Si8 Nb2 alloy. The roie of electromagnetic field has been investigated in t hesolidfotion of undercooled melt. The observations and analysis show that electromagnetic field has little effect on theundercooling, but has obvious effect on the nucleation and growth of crystal. The laws of nucleation and crystal groWth in theelectromagnetic field are different from these in solidification. It is believed that electromagnetic field can further increasethermodynamic undercooling degree