Different crystallographic planes, at a gas-metal interface, have different surface energy. To grow the (100) grains of 6.5wt%Si-Fe alloy preferentially, it was heat-treated in the atmosphere of sulfur by using the surface energy. When the specimen is heat-treated for 1 hour at 1175℃ by using the atmosphere of sulfur produced by heating at 75℃, (100) grains were grown to 3.5㎜. Owing to the growth of (100) grains, the coercive force was decreased to 2.1A/㎜, and the magnetic induction at 800(A/㎜) was increased to 1.61T.