The amorphous iron-boron alloy can be prepared very easily by a room temperature solid-solid reaction of the FeCl3.6H(2)O, CrCl3.6H(2)O and KBH4 powders. The characterizations show that the product is mainly composed of amorphous iron-boron alloy nanoparticles. Fe-57 Mossbauer spectra at 84 and 295 K show that there are three kinds of Fe-containing components in the sample. There are the superparamagnetic relaxation in Mossbauer spectra and the continuous distribution of internal magnetic field in the iron-boron alloy. (C) 2004 Elsevier B.V. All rights reserved.