Abstract: In order to obtain the optimal condition for biodiesel production from ultrasonic enhanced transesterification and provide reference for industrialisation of biodiesel, the effects of density of ultrasonic power, reaction temperature, aomunt of catalyst and molar ratio of methanol to oil on the ultrasonic enhanced transesterification catalyzed by potassium hydroxide were investigated, and the parameters for biodiesel production by using response surface method (RSM) were further optimized. The results showed that under the optimal condition i.e density of ultrasonic power 54.7 W/L, reaction temperature 34℃, amount of catalyst 1.3%, molar ratio of methanol to soybean oil 6:1, the content of methy-ester in transesterification was 99.68%, meanwhile, the experimental value of the content of methy-ester was 99.56%. The optimal experimental result of RSM is suitable for biodiesel production technologies based on transesterification catalyzed by alkali, and it can be used to predict the content of methy-ester in different conditions of transesterification catalyzed by alkali.