Abstract: In order to study thermal oxidative aging behavior of cross-linked polyethylene (XLPE) insulating materials,accelerated aging tests were carried out under the condition of high temperature and oxygen aging.By Fourier transform infrared spectroscopy (FTIR),differential scanning calorimetry,thermogravimetric analysis and scanning electron microscopy,changes in molecular structure,melting crystallization behavior,oxidation resistance,microstructure,electrical properties and mechanical properties of XLPE insulating materials were analyzed during high temperature and oxygen aging process.Results showed that with the consumption and loss of antioxidants,aging degree of XLPE continuously deepened,which showed that a large number of oxygencontaining groups were generated during thermal oxidative aging of polyethylene,leading to a decrease in molecular chains regularity,crystalline performance and thermal oxidation resistance,a decline in electrical performance,and severe surface damage to insulating material.Combined with thermal analysis kinetics,activation energy of XLPE insulating material was 119 kJ·mol^-1,and thermal oxidative aging life at 90℃ of which was calculated to be about 68.2 years.