A combination of ultrasonic and chemical catalyst affects to the transesterification reaction rate of palm oil conversion to biodiesel is investigated in a 5 Liter capacity reactor equipped with the heater and temperature controller and the 42 Hz ultrasonic generator of 35 watt with process parameters of (a) reaction temperature, (b) methanol to palm oil ratio, (c) and the amount of chemical catalyst and (d) duration of the ultrasonic activation. The result shows that by combining the ultrasonic and chemical catalyst in the palm oil transesterification processing increases the chemical reaction rate, the higher the frequency of the ultrasonic activation used, the higher the biodiesel conversion.The transesterification operating process condition of 60 to 70 oC, Methanol to palm oil ratio of 5, reaction duration time of 60 minute, and catalyst activation of 30 minute, using a 42 KHz , 35 watt ultrasonic, may be applied to produce biodiesel with a conversion as high as 94% for palm oil feed stock and 91% for coconut oil feedstock