Castor oil is an alternative feedstock in biodiesel production, due to the abundant availability of raw materials, especially in Indonesia. To utilize the number of jatropha trees, it will be used as raw material, it will be used as biodiesel. Vegetable oils have a higher viscosity than fossil diesel fuel that will greatly affect combustion in the combustion engine diesel, the use of vegetable oil as an alternative biodiesel material must first be through the transesterification process. Transesterification is the conversion process between methanol and triglycerides to alkyl ester and geliserol. In this process the vegetable oil is reacted converted to methyl ester (biodiesel) with methanol and catalyst (KOH) through a transesterification process using a heating device. In this research, the first step in a biodiesel production is started from coconut oil with 1200 ml volume which was processed in transesterification using methanol 15% from volume of oil and the catalyst used is Potassium Hydroxide (KOH) with a ratio of 1% of the oil volume. The process of jatropha curcation with a mixture of methanol and KOH catalysts used four variations of reaction time (30 min, 60 min, 90 min, 120 min) and two temperature variations (55°C and 65°C). The results of this study indicate that the best combination, whether the density value, viscosity, flash point and heat value are at transesterification temperature 55℃ with 30 minutes stirring time. However, the resulting value mesih does not meet SNI value standards as fuel.