Abstract: The biodiesel production through transesterification reaction from tallow with methanol was studied, and KOH was used as catalyst. Combined artificial neural network with orthogonal experimental design, the reaction factors such as molar ratio of methanol to oil, catalyst amounts, reaction time and reaction temperature were investigated. On the basis of the orthogonal experimental results, the reaction conditions were simulated and optimized using artificial neural network, and the optimum reaction conditions were obtained as follows: reaction temperature was 70℃, molar ratio of methanol to oil was 10.5︰1, the amount of catalyst was 1.1% (based on the weight of oil) and reaction time was 90min. Under the optimum reaction conditions, the transesterification reaction conversion ratio is 94.16%, which is higher than the result of 93.17% obtained from orthogonal experiments.