The Ni rich amorphous boride nanoparticles can be prepared very easily by the solid-solid reaction of the NiCl2 and NaBH4 powders at room temperature. XRD, DTA-TG, FESEM, TEM, and selected-area electron diffraction characterize the resultant nanoparticles. The results show that the resultant is mainly composed of the amorphous Ni-B alloy nanoparticles with an average diameter of 15-25 nm. © 2011 American Institute of Physics.