Abstract: The long-term accelerated aging test in laboratory environment has been conducted on the composite insulating materials of actual rotating coils subjected to combined stresses including electrical, thermal, mechanical vibration and thermal cycling factors under simulated conditions. The dynamic mechanical experiment of composite insulating materials has been carried out in different aging periods using Dynamic Mechanical Analyzer (DMA) and the relationship between mechanical parameters and the aging time of composite insulating materials is also analyzed in this paper. Based on the Eyring absolute reaction speed theory, a method calculating the apparent activation energy of glass transition (AAEGT) is developed, which is used to calculate the AAEGT of composite insulating materials according to its mechanical dissipation curve in different aging periods.