In this paper, calcined river-snail shell was used as a novel solid base catalyst in the transesterification of soybean oil with methanol for biodiesel production. The calcined river-snail shell was characterized using field emission scanning electron microscope and X-ray diffraction. Effects of transesterification process variables were investigated. The results indicated that river-snail shell calcined at 800 °C catalyzed the transesterification of soybean oil for biodiesel with a yield over 98 % under the conditions including catalyst of 3.0% (w/w), a molar ratio of methanol/oil of 9:1, reaction time of 3 h, and reaction temperature of 65 °C. As a low-cost green catalyst, calcined river-snail shell could not only minimize the environmental wastes resulted from the solid shell, but also reduce the production costs of biodiesel.