Fe3O4 magnetic nanoparticles supported on modified montmorillonite clay, were utilized for catalytic performance for the synthesis of different 3,4-dihydropyrimidin-2(1H)-ones under green reaction condition. The modification of Montmorillonite K10 clay was carried out with HCl under controlled conditions for generating a high surface area porous matrix which acts as support for the in situ generation of Fe3O4- nanoparticles. The synthesized nanocomposite material was characterized by powder XRD, TEM, N2 adsorption-desorption and XPS analysis. The catalysts can be recycled and reused several times without significant loss of their catalytic activity.