Abstract. The biodiesel production using KOH-Montmorilonite catalyst in microwave-assisted reactor catalyst through transesterification has been carried out. The transesterification process was carried out using the ratio of moles of methanol/oil, the amount of catalyst, the variation of time, and the variation of the weight of the catalyst. The results showed that the optimum biodiesel obtained was at a mole ratio of methanol/oil 1:9, the amount of catalyst was 3%, the variation of time was 45 minutes, and the variation of temperature was 65 oC with a biodiesel conversion is 50.26%.