Epoxy resin is the most widely used insulation material for power equipment, and its fire hazard characteristics are related to the safe and stable operation of power equipment throughout its entire life cycle. However, the fire hazard characteristics of epoxy resin under aging conditions are not yet clear. Therefore, this article first selects the influencing factors (humidity, heat) that dominate the aging of insulation materials for multi factor coupled aging tests, and further uses oxygen index testing and horizontal/vertical combustion testing to study the effect of different aging degrees on the flame retardant performance of epoxy resin. Research has found that the horizontal fire hazard classification of epoxy resin samples tested in this experiment after 0–56 days of wet heat aging is HB40, and the horizontal combustion performance is not affected by the wet heat aging time; The vertical fire hazard classification is V-1, but with the increase of damp heating aging time, the total residual flame and residual ignition time show a downward trend, indicating that the epoxy resin material has better flame retardant performance after wet heat aging; The oxygen index test results show that the overall flame retardant of epoxy resin is good, and the it gradually increases with aging time. After one day of aging, the oxygen index tends to saturation. Further analysis was conducted on the reasons for the improvement of flame retardant of epoxy resin after wet heat aging from the perspective of the volatilization of combustible additives and the increase in bulk crosslinking density. Finally, the study proposes the identification of fire hazard levels for aging electrical equipment, and it is necessary to develop fire hazard testing methods that are more in line with the characteristics of electrical fires.