Production of castor oil biodiesel has been done by transesterification process. The castor oil was previously tested for titration and produced 77,78 % free fatty acid. The process was done in a autoclave by mixing the materials of castor oil to methanol in 1:12 mole. The reaction use 4 % and 8 % of PSS catalyst in 1200C for 6 hours. The solution was neutralized by ammoniac and estracted by n-hexane. The transesterification resulted in 2 layers: upper layer containing methyl ester (FAME) and the lower layer containing residual glycerol and methanol and than separated. The upper layer of the separating funnel contained FAME added sufficiently by n-hexane, and then washed by aqueous repeatedly. The filtrate was distillated by an usual distillation and than vacuumed and the residueweighted. FAME has finished then tested with Gaskromatografi(GC) to determine the content of the results of the reaction, thebreakdown of methyl ester= 93.35%, monogiserida= 0.348%,diglycerides= 0.448% and triglisrida= 0.685%.