Magnetic nanoparticle (MgFe2O4@CaO) catalyst coated by CaO was successfully synthesized by using the alkali precipitation with the presence of sodium dodecylbenzenesulfonate (SDBS). The obtained heterogeneous catalyst was highly efficient for the synthesis of biodiesel with soybean oil and methanol as raw material. Furthermore, under the reaction conditions of catalyst dosage 1.0 wt.%, methanol:soybean oil ratio of 12:1, reaction temperature 70 degrees C, reaction time 3 h, the MgFe2O4@CaO catalyst showed the better activity, the higher acid-resistance and the better water resistance in the transesterification reaction compared with pure CaO. The MgFe2O4@CaO catalyst was characterized by XRD, TEM, VSM and CO2-TPD. The excellent performance of MgFe2O4@CaO catalyst with the yield of biodiesel 98.3% could be mainly attributed to the synergy between calcium and magnesium. Moreover, the catalyst was simply recovered by an external conventional magnet and recycled after completion of reaction, and there was no observation for the significant decrease of the catalytic activity. After further reused for 5 times, the yield of FAME could still reach 89%, which indicated that the MgFe2O4@CaO catalyst had a good stability and recyclability. The development of MgFe2O4@CaO as a novel heterogeneous catalyst would provide an environmentally friendly manner for biodiesel production. (C) 2015 Elsevier Ltd. All rights reserved.