In this work, calcium ethoxide is proposed as a catalyst for the transesterification of soybean oil to biodiesel with methanol and ethanol. First, calcium ethoxide was synthesized through a calcium reaction with ethanol. Then, its physical and chemical characteristics were determined using instrumental methods such as Brunauer-Emmett-Teller surface area measurements, scanning electron micrographs, and particle size distribution measurements. The effects of the mass ratio of catalyst to oil, the molar ratio of methanol to oil, and the reaction temperature were studied to optimize the reaction conditions. The experimental results showed that the optimum conditions are a 12:1 molar ratio of methanol to oil, the addition of 3% Ca(OCH2CH3)(2) catalyst, and a 65 degrees C reaction temperature. A 95.0% biodiesel yield was obtained within 1.5 h in these conditions, and the activation energy was 54 149 J/mol. It also indicated that the catalysis performance of calcium ethoxide is better than that of CaO. Besides, a 91.8% biodiesel yield was obtained when it catalyzed soybean oil to biodiesel with ethanol.