Abstract: To meet the demand of improving the thermal oxidation stability of trimethylolpropane trioleate (TMPTO), the Raman feature peak temporal variation law of the TMPTO and the oil sample with addtion of alkyl diphenylamine antioxidant of butylated, octylated diphenylamine (T557) and dinonyl diphenylamine (T558) during the high temperature oxidation process was investigated using the combination of DXR laser microscopic Raman spectrometer with Linkam FTIR600 temperature control platform. The molecular structure characteristics of TMPTO during the thermal oxidation process and the mechanism of alkyl diphenylamine antioxidant have been further discussed. The results show that the Raman peaks of =C-H, C=C and -CH₂- decreeased gradually with the oxidation time and the structure variation of C=C followed the rule of first order kinetics. At a constant temperature of 175 ℃ and continuous oxidation condition, T557 and T558 alleviated the Raman peak attenuation of =C-H, C=C and -CH₂- in TMPTO molecule. The thermal oxidation reaction rate constant of C=C decreased from 0.14 h^-1 to 0.02 h^-1.