A novel heterogeneous solid base catalystwas preparedwith the support of Al-Ca hydrotalcite, the load of K2CO3 and successfully applied to the transesterification of soybean oilwith methanol to biodiesel (fatty acidmethyl esters).The prepared catalysts were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction,scanning electron microscopy, energy dispersive X-ray spectrometer, transmission electron microscopy,thermogravimetry analysis, differential scanning calorimetry and the Hammett indicator methods. The results indicated that K2CO3 loaded to Al-Ca hydrotalcite was decomposed into catalytic active compositions of K2O and Al–O–K. The effect of various parameters such as reaction temperature, amount of catalyst, reaction time and the amount of methanol on the catalytic active was investigated. The optimal reaction conditions were obtained by this experiment: a methanol/oil mole ratio of 13:1, a reaction temperature of 65 °C, a catalyst amount of 2.0wt.% and
a reaction timeof 2.0 h. The catalyst has longer lifetimeand biodiesel yield could be still over 87.4%
after being used for four cycles.