Abstract: By studying the composition of vitamin E in peanut oil,eight kinds of vitamin E isomers were detected,with the total content of 281.78 μg / g,in which α- tocopherol occupied 53.7%.Under the base of above results,the effects of endogenous substance( α- tocopherol) and extraneous factors( oxygen,temperature) on the oxidation stability of peanut oil were studied according to the changes of peroxide value,p- anisidine value,DPPH radical scavenging capacity. The results showed that: in the storage period,low concentration( 0.01%) of α- tocopherol delayed the primary oxidation process of peanut oil effectively; while in the secondary oxidation process,it didn't show any antioxidant effect on the peanut oil. However,α- tocopherol with high concentration( 0.02%) promoted oxidation process. Therefore,the additive amount of α- tocopherol should be strictly controlled. Compared with adding α- tocopherol and BHT in peanut oil,treatment of low temperature,sealing and filling with nitrogen could delay the oxidation process of peanut oil more effectively,which is a convenient,efficient and safe measure for the preservation of peanut oil.