A systematic study of crystallization characteristics in the Fe-Ni-B amorphous alloys has been carried out by annealing at temperatures ranging samples from room temperature to 970K in vacuum. The analysis of the Mo ssbauer spectrum along with supporting X-ray diffraction and DSC measurements is presented. By the Mo¨ssbauer spectroscopy, the crystallized phase in the Fe_(80-x)Ni_xB_20 amorphous alloys consisted of γ-(FeNi), t-Fe₃B or γ-(FeNi), o-(FeNi)₃B, t-Fe₃B for x≤30, γ-(FeNi) and o-(FeNi)₃B for x=40. Two-step crystallization was observed in the alloy system of (Fe_(0.5)Ni_(0.5))_(100-x)B_x for x＜18(amorphous→amorphous+γ-(FeNi)→γ-(FeNi)+o-(FeNi)₃B) and o-(FeNi)₃B was observed for x>20. The t-Fe₃B phase is unstable and changes to t-Fe₃B at higher temperature. The phase transition for t-Fe₃B to t-Fe₂B sensitively depends on the Ni content in the Fe_(80-x)Ni_xB_20 amorphous alloys with x≤30. Increasing the amount of either Ni or B in the alloys, it is easier for the o-(FeNi)₃B phase to be found. The results indicate that a chemical ordering occurs between the metal(Ni) and metalloid(B) atoms that decreases the crystallization temperature and activation energy.