In this study, catalyst Pd/Fe3O4 based on magnetic body with the size of 8 nm was prepared and characterized by TEM, HRTEM, XPS and VSM methods. The results show that Pd-0 atom produced after the first reduction is bound to APTS-coated Fe3O4 nanoparticles by the coordination of -NH2 ligand with Pd-0 and then grows into bigger clusters with the increase in the reduction times. However, when the reduction is performed for more than three times, Pd-0 atom produced in subsequent reduction is dispersed in aqueous solution instead of depositing around preexisting Pd-0 atom or clusters. In order to further investigate its catalytic behavior, Heck reaction of the cross-coupling of acrylic acid with iodobenzene was employed. The activity measurements show that the product yield decreased greatly from 81% for the first times to 53% for the fifth times and then kept constant in the subsequent re-use. One of the important reasons for this is that the catalyst aggregates into big particle and becomes more difficult to be dispersed with the increase in reaction times. In a word, this preliminary work provides the primary understanding of the catalyst based on Fe3O4 nanoparticles and its application in Heck reaction. (c) 2005 Elsevier B.V. All rights reserved.