Afandi, TrisnoNurhayatiAwaluddin, Amir2016-05-162016-05-162016-05-16wahyu sari yenihttp://repository.unri.ac.id/xmlui/handle/123456789/8383CaO is a basic catalyst which is frequently used for the synthesis of biodiesel. The development of catalyst especially CaO has become attractive topic for research in order to obtain good catalytic activity so that biodiesel produced will be increased. In this study, the CaO was synthesized from decomposition reaction of blood cockle shell at 900°C for 5 hours. KOH was impregnated into CaO by simple wet impregnation method (percentage K: 1%, 3% dan 5% (w/w) CaO). The catalyst was then characterized by XRD, adsorption methylene blue, Atomic Absorption Spectrophotometer and titration. The activity of catalysts was tested by synthesis of biodiesel using waste cooking oil as feedstock at weight of catalyst 3%, mole ratio of oil:methanol 1:6, temperature of reaction 60°C for 3 hours. Biodiesel produced by blood cockle shell catalyst without impregnation was 82,53%, while biodiesel produced by blood cockle shell catalyst impregnated KOH 1%, 3%, and 5% were 77,96%, 74,94%, and 81,5% respectivelyenBiodieselblood cockle shellimpregnationtransesterificationstudent Paper Post Degree