The Ca-Mg mixed oxides were synthetized from a new method using calcium oxalate and magnesium oxalate as the precursors for transesterification of soybean oil. To elucidate their composition, morphology and basic properties, the resulting materials were characterized using: XRD, SEM, TEM, CO2-TPD and Nitrogen adsorption desorption. The results showed that the catalyst with neat blocky structure had better water-resistance compaied to the pure calcium oxide. And the CaO-MgO exhibited higher amounts of basic site and provided higher catalytic activity in the methanolysis process. The highest biodiesel yield reached 98.4% over CaO-MgO with a Ca-to-Mg molar ratio of 1:3 under the optimal reaction conditions: 1.0 wt% of catalyst adding, 12:1 of methanol/oil and reacting at 70 degrees C for 2 h. Hopefully, this kind of stable solid base catalyst could confirm the yield of FAME still above 90% after using 5 times which demonstrated the good reusability of mixed oxide CaO-MgO catalyst. (C) 2016 Elsevier B.V. All rights reserved.