Supported solid base catalyst CaO/MgO/gamma-Al2O3 made by impregnation method was used in the transesterification of palm oil with methanol to prepare biodiesel fuel. The optimal conditions were found to be a molar ratio of methanol to oil of 9, a catalyst dosage of 3.5%, a reaction temperature of 65 degrees C, and a reaction time of 3 h. A hammer indicator method was employed to determine the catalyst alkaline strength and gas chromatography was used to analysis the component of biodiesel. In the end, the quality of the obtained biodiesel fuel met the requirement of GB/T 20828-2007.