A study to assess acid value (AV) in palm oil and coconut oil during storage was conducted. The study was conducted three stages: extraction methyl gallate from the surian fruits, oil extraction, and oil quality testing by determining the acid value (AV). To test the quality of the oil, the samples were added of methyl gallate and kept at temperature 40˚C for 30 days. As a comparison used synthetic antioxidant, butylated hydroxytoluene) (BHT), tert-butyl hydroquinone (TBHQ). Analysis of acid value (AV) is performed every 5 days, from day 0 to day 30. The results showed that methyl gallate derived from of surian fruit extract could prevent the increasing of acid value of palm oil and coconut oil during storage at 40˚C.