Abstract: In order to study free radical chain reaction of peanut oil during accelerated oxidation,the oxidation process of peanut oil was investigated by electron paramagnetic resonance spectroscopy(ESR). The results demonstrated that large amounts of alkyl radicals(R·) as well as a small number of alkoxy radicals(RO·) and peroxide radicals(ROO·) were produced in peanut oil during accelerated oxidation process. A comparative study was conducted to determine the oxidation stability of peanut oil with different antioxidant by two different instruments:ESR and Rancimat(a classic method for determination oxidation stability of oil). The results showed that the lagtime of ESR was consistent with the IP of Rancimat,that is,peanut oil which was added 0.02%TBHQ and 0.01%citric acid had the smallest yield of free radicals,the longest lagtime and IP. Moreover,there existed an excellent linear relationship between lagtime and IP,and the regression equation was Lagtime=79.724IP-165.630(R2=0.9688). From the above,ESR was an useful method for prediction of Rancimat and also could be used as a method for evaluating the oxidation stability of peanut oil.