Abstract: Effects of various factors on bio-diesel preparation by ultrasound and enzyme are studied in this article,using corn oil,ethanol and Lipozyme TL IM as the major raw materials.Comp-arison between three biodiesel preparation methods is done,including shake bed method,with and without ultrasound.Bio-diesel yield was first increased,and then decreased with the increase of ethanol dosage,reaction temperature or solvent petroleum dosage.It was continuously improved as the enzyme dosage went up or reaction time was lengthened.The optimum reaction parameters were: molar ration of corn oil to ethanol 1:1,reaction temperature 60℃,enzyme dosage 10%,ration of solvent usage(mL) to mass of corn oil(g) 1:1,and enzymatic reaction time with ultra-sound 3h.At the same reaction temperature,the bio-diesel yield was improved evidently with ul-trasound.Compared the reaction with and without ultrasound,as well as the action of shake bed,it rose up by 27%～33% and 6%～15% respectively.However,the optimum reaction temperature was not changed by ultrasound.