Abstract: This study focuses on the effect of mixing on transesterification in biodiesel production. A stirred-tank reactor assisted by ultrasonic wave was used in experiment. Crude Palm Oil (CPO) was used as raw material in transesterification. The optimum condition for giving the highest yield is at temperature of 60°C, CPO to Methanol ratio 1:9 and Na2CO3/ceramic 3% by weight of CPO. The kinetic model fitted experimental data well and can be used to describe the mixing performance. Biodiesel production was strongly affected by the level of mixing, thus the stirring speed. At 300 rpm stirring speed, productivity of biodiesel is higher than 90% conversion of triglyceride. Ultrasonic wave did not increase biodiesel conversion but significantly enhanced the reaction rate.