Biodiesel was obtained through transesterification of animal oil and ethanol under the catalysis of SO42- / TiO2 We have inspected the activation of SO42- / TiO2prepared under different dipping vitriol concentration,baking activation temperature. The optimum conditions to prepare SO42- / TiO2are; dipping vitriol concentration of TiCl4 hydrolysis product is 1.5 mol / L, baking activation temperature for this catalyst takes 500°C. It can guarantee the catalyst has a smaller size and a higher load of vitriol. With animal oil as raw materials, ethanol as transesterifying agent and SO42- / TiO2as catalyst, the influence of reaction time, mass ratio of ethanol to oil and the dosage of catalyst were investigated. Optimum condition to obtain biodiesel was studied through orthogonal experiment, and it is listed as follow: mass ratio of ethanol to oil is 1.5:1.0, dosage of catalyst is 30 g SO42- / TiO2versus per 100 g animal oil, and reaction time is 8.0 h when reaction temperature is controlled as 80°C. The yield of biodiesel is 0.796 g/g under the above condition. SO42- / TiO2can be used as an effective catalyst during transesterification of animal oil and ethanol, and it can be reused