The wetting behavior of liquid Sn on three types of Fe 7 8 B 1 3 Si 9 substrate, an amorphous substrate and two types of pre-annealed substrate, was studied by the sessile drop technique between 350 and 450 o C. The equilibrium contact angle of the amorphous Fe 7 8 B 1 3 Si 9 substrate did not decrease monotonically with increasing temperature, which is evidently different from that of polycrystalline alloy substrate. Pre-annealing of Fe 7 8 B 1 3 Si 9 substrate made its wettability very poor when the wetting temperature was lower than the pre-annealing temperature. However, when the wetting temperature was higher than the pre-annealing temperature, pre-annealing of substrate had little effect on the equilibrium contact angle. These were related to the effect of crystallization reaction of Fe 7 8 B 1 3 Si 9 on interfacial tension and interfacial reaction.