Abstract: The long-term aging performance of cross-linked polyethylene (XLPE) insulation material for high-voltage power cables will determine the operating reliability and working life of cables. This work aims to evaluate the long-term working reliability of the domestic 220 kV XLPE insulation material. An imported 220 kV XLPE cable insulation material was taken as a reference, and the electrical and thermal aging characteristics of domesticaly trial-produced 220 kV cable material were comparatively studied. For the two 220 kV AC cable insulation materials, the long-term thermal-oxidative aging tests were carried out, and the mechanical properties, infrared spectroscopy and differential scanning calorimetry (DSC) were used to characterize the thermal-oxidative aging behavior of the materials. Then the constant stress electrical aging tests were carried out using sheet samples. According to the aging life theoretical model, the thermal-oxidative aging and electrical aging lives of the two 220 kV XLPE insulating materials were evaluated. The thermal-oxidative aging test results show that the oxidation rate of domestic trial-produced material is slower, however, its crystallization and mechanical property are relatively inferior. If when the mechanical property is dropped to 30% of the initial value is set as the insulation failure criterion, the thermal-oxidative aging life of imported and domestic materials are 32.85 years and 29.14 years, respectively. The thermal-oxidative aging resistance of domestic trial-produced material is slightly inferior to that of imported material. The constant stress long-term electrical aging test results show that the n indexes of electrical aging life for imported material and domestic trial-produced material are 16.84 and 17.03, respectively. The electrical aging resistance of the domestic trial-produced material is relatively better. The long-term aging performances of domestic 220 kV cable insulation material have reached the level close to that of imported materials.