Naphthenic acid is a complex of carboxylic acids (various low-molecular-weitht fatty acids believed to have cyclopentane ring mainly) presented in acid crude oils. They often cause serious problems such as pipeline corrosion in processing crude oils. As oil price has rapidly increased recently, utilization of acid crude oil became rather active across the world. Thus, finding an economic way to reduce naphthenic acids from crude oil turned out to be very important for oil refinery industries to make the cost balanced. Among the technologies, catalytic decarboxylation of naphthenic acids seems promising and may provide a solution for that purpose. It has been reported that various metal oxides are active toward the decarboxylation. However, their poor stability under reaction condition – high temperature and high acidic environment – makes them inappropriate for the treatment of acid crude. In this study, various kinds of mixed metal oxides of alkaline earth metal with alumina or silica were prepared in various ways, and their long term stabilities were compared with the alkaline earth metal oxide.