Epoxy resin has a wide range of applications in electrical equipment due to its good electrical, and thermal properties. The long-term aging performance of epoxy insulation materials is a key parameter to determine the service life of electric equipment. To study the aging characteristics of epoxy resins and to research the mechanism of thermo-oxidative aging effects in thermal properties of epoxy resins, the epoxy specimens in this paper were accelerated aging at $250^{\circ} \mathrm{C}$ for 10 days. The chemical structure, glass transition temperature and thermal decomposition parameters of epoxy materials with different aging times were tested by FTIR, DSC and TGA experiments. It was revealed that the $T_{\mathrm{g}}$ of the samples showed uptrend and then stabilizing; the onset decomposition temperature and the fastest decomposition temperature of the materials did not change with aging time, while the rate of thermal decomposition showed a declining trend.