Used cooking oil is leftover cooking oil from food frying processes that have been usedrepeatedly. This resulted in increased high free radical and fatty acid content which can be harmfulto health. One attempt to reduce oil damage is with the addition of antioxidants. Curcumin is anantioxidant contained in turmeric. Curcumin is an antioxidant phenol which have many double bondsthat can capture free radicals, which can slow down the increase in the peroxide and acid number ofused cooking oil. The purpose of this study was to determine the effect of turmeric powder on levelsof acid number. This type of research is experimental by the number of samples in each treatmentand as many as 16 samples. Formulation of the problem of this study is whether there is the effect ofturmeric powder on levels of acid value on used cooking oil. The examination results on the levels ofacid number of used cooking oil shows the average levels of the acid number of used cooking oilwhich without the provision of turmeric powder is as high as 0,641, while the one with the provisionof turmeric powder is as high as 0,349. Statistical analysis by t test showed the effect of turmericpowder on levels of acid value on used cooking oil with value of p (sig) = 0.000 which is less than0.05. Therefore, the turmeric powder can inhibit the decrease of acid number on used cooking oil sothat the oil quality is maintained