A nano-magnetic catalyst KF/CaO-Fe3O4 was prepared by a facile impregnation method. The magnetic property of the catalyst was studied by vibrating sample magnetometer (VSM). The results demonstrated that the catalyst was ferromagnetic, and it could be recovered by magnetic separation. The nano-magnetic catalyst was also characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface area analyzer. It was found that the catalyst possessed a unique porous structure with an average particle diameter of ca. 50 nm. Besides, the factors affecting biodiesel yield were investigated, and a desired fatty acid methyl esters yield over 95% was obtained under the optimal conditions. (C) 2011 Elsevier Ltd. All rights reserved.