Abstract: In this paper,the regularity of annealing embrittlement for amorphous alloys Fe₈₀B_20-xSi_x (x=6, 8, 10, 12) is studied.The effects of composition,purity of the raw materials, thickness and the surface condition of the ribbons on annealing embrittlement of the alloys are shown.Annealed at lower tmperature,Fe-based amorphous alloys have already become brittle. This annealing embrittlement is caused by structural relaxation which is controlled by the metastability of amorphous alloys.