The local structures and the devitrifications of Ni 70 B 30 nano-amorphous alloys prepared by chemical reduction method were studied by in-situ X-ray absorption fine structure (XAFS). The results indicate that the preparation temperature strongly affects the local structures of Ni 70 B 30 amorphous alloys. The coordination geometry surrounding Ni atoms is a structure of amorphous Ni-like for the Ni 70 B 30 (273K) while the Ni 70 B 30 (313K) has amorphous Ni 3 B-like structure. In-situ XAFS analysis revealed that the Ni 70 B 30 amorphous alloy prepared at the low temperature of 273K is directly crystallized into the metallic Ni in a wide temperature range from 498 to 598K. However, the crystallization of the sample prepared at the high temperature of 313K is accomplished in two steps: the generation of intermediate product of crystalline Ni 3 B starting from 548K and finishing at about 573K; the unique formation of crystalline Ni at about 598K.