Biodiesel is manufactured by transesterification of animal fat or vegetable oil. The reactants ( oil and methanol) and the products ( fatty acid methyl ester and glycerol) are partially mutual soluble in the reaction process. Intersolubility of the reaction components is essential data for the production design and process operation. In this work, the Jatropha curcas L. oil ( oil) has been transesterified to give Jatropha curcas L. oil methyl ester ( FAME). The inter-solubility of FAME + methanol + glycerol, oil + FAME + methanol, oil + glycerol + methanol, and oil + FAME + glycerol in the range from 298.15 K to 333.15 K has been conducted. Methanol is completely soluble in both FAME and glycerol but is not soluble in oil. With an increase in the mass fraction of FAME, the solubility of methanol in the oil + FAME phase increases. The transesterification reaction is carried out in the methanol phase, and as a result, the reaction shows an induction period. When FAME content increases to 70%, the oil + methanol + FAME mixture becomes a homogeneous phase. Glycerol has a low solubility in both oil and FAME and, hence, is easily separated from the final product of biodiesel. The solubility is temperature insensible.