The amorphous Co-B particles were prepared from cobalt nitrate and potassium borohydride. Ethanol-thermal treatment has been used to promote the crystallinity of Co-B particles. Both the amorphous and crystallized Co-B particles were characterized by X-ray powder diffraction (XRD), scanning electron micrograph (SEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), specific surface area (S-BET), CO temperature-programmed desorption (TPD), and magnetic performance test. After crystallization, the synergistic effect between Co and B, the structure stability, and the magnetic property of Co-B enhanced while the activation energy in cinnamaldehyde (CMA) hydrogenation decreased. Furthermore, the conversion of cinnamaldehyde (CMA) increased from 5% to 57%. The hydrogenation of the C=C bond in cinnamaldehyde (CMA) is favored for the amorphous Co-B particles while the hydrogenation of the C=O bond is preferred for the crystallized Co-B particles. After 13 cycles, the crystallized Co-B particles remain higher cinnamaldehyde (CMA) conversion and cinnamyl alcohol (CMO) selectivity, which is attributed to their good structure stability and the novel magnetic method for recycle; while the cycle performance of amorphous Co-B particles is poor due to their instable structure. (c) 2006 Elsevier B.V. All rights reserved.