This paper discusses the influence of lightning transient impact on the overvoltage of the transformer’s high-voltage winding, and analyzes its voltage waveform and short-circuit impedance characteristics. By establishing the RLC lumped parameter circuit model and using numerical simulation, the distribution of overvoltages at different nodes and the voltage difference between adjacent nodes are studied in depth. The research results show that lightning impact significantly affects the electrical performance of the transformer, and short-circuit impedance plays a crucial role in the stability of the equipment. In addition, this paper proposes an overvoltage calculation framework suitable for lightning conditions and provides suggestions for relevant parameter extraction to support subsequent research and application. Finally, the paper points out the direction of future research, including optimizing circuit models and combining intelligent monitoring strategies, aiming to improve the safety and reliability of power systems.