Abstract: The distributions of fatty acid methyl esters in several biodiesel fuels prior and post to accelerated oxidation were determined by EN14103 standard method, and the results showed that the contents of linoleic acid methyl ester and linolenic acid methyl ester in biodiesel were the key factors affecting the oxidative stability of biodiesel. The oxidation of biodiesel was further studied through determining the apparent activation energy of biodiesel oxidation. Results showed that the apparent activation energies of oxidation reactions for biodiesel fuels having various oxidative stabilities were varied; adding antioxidant into biodiesel could increase the apparent activation energy of oxidation reactions significantly, as a result, the oxidation of biodiesel was postponed and its oxidative stability improved.