A study of the effect of annealing temperatures and time periods on the hyperfine field distributions of Fe79B16Si5 metallic glass near and below the crystallization temperature was carried out using Fe-57 Mossbauer spectroscopy. The effect of crystallization during annealing as a function of annealing time on the average hyperfine magnetic held, < H >, and the relative change of the probability of hyperfine fields, P < H >, with respect to that of the as-received sample are also discussed.