Abstract: The late effect of high-altitude nuclear electromagnetic pulse (E3 effect) seriously affects the operation of power equipment and even paralyzes the power supply system by generating DC bias magnetism. In view of this phenomenon, this paper simulates the late environment of high-altitude nuclear electromagnetic pulse, establishes a transformer model, and carries out a comprehensive analysis of the impact of DC bias on the transformer, including the vibration displacement inside the transformer, the sound pressure level of the transformer, and the temperature increase of the core inside the transformer. The simulation results show that with the increase of the current introduced into the transformer in the E3 stage of the nuclear explosion electromagnetic pulse, the displacement, noise and sound pressure and temperature rise of the transformer core will increase rapidly, and it is very likely to exceed the relevant threshold of the transformer, thus causing damage to the transformer.