Vitamin E octenylsuccinate（VE-OS ester），obtained from the esterification of VE and octenylsuccinic anhydride（OSA），was used for the structure identification by infrared spectroscopy（IR） and nuclear magnetic resonance（NMR）.New absorption peaks at 1 860，1 776,1 755 cm-1 were found in IR，suggesting that the structure of the carboxylic acid ester extsts.1H NMR spectrum showed that the hydroxy group of VE was substituted because of the disappearance of the signal of hydroxyl group.The signal of H-9 distributed at 3.05 ppm and 3.20 ppm，and C-11 and C-12 had four peaks at 170-180 ppm in 13C NMR spectrum，showing that VE-OS ester had two isomers（a and b），and isomer a was formed easier after the analysis of NMR integrals.Using density functional theory（DFT） B3LYP/6-311++g** calculation，the configurations of VE-OS ester were optimized，and the results implied isomer a is more stable than b，which agreed well with the analysis data.Different high performance liquid chromatographic（HPLC）methods were also compared for quantitative analysis of VE-OS ester.