CaAl layered double oxides (LDO) were prepared by co-precipitation and calcined at 750 degrees C, and then applied to biodiesel production by transesterification reaction between methanol and soybean oil. Compared with characteristics of CaFe/LDO and CaAl/LDO, CaFeAl/LDO had the best performance based on prominent catalytic activity and stability, and achieved over 90% biodiesel yield, which stayed stable (over 85%) even after 8 cycles of reaction. The optimal catalytic reaction condition was 12: 1 M-ratio of methanol/oil, reaction temperatures of 60 degrees C, 270 rpm stirring rate, 60 min reaction time, and 6% weight-ratio of catalyst/oil. In addition, the CaFeAl/LDO catalyst is insoluble in both methanol and methyl esters and can be easily separated for further reaction, turning it into an excellent alternative for biodiesel synthesis. (C) 2015 Elsevier Ltd. All rights reserved.