In order for power transformers to operate safely and reliably, it is important to reasonably design the internal insulation structure of transformers, especially the insulation of transformer coils must be able to reliably withstand the effects of atmospheric overvoltage, long-term working voltage, operating overvoltage and transient overvoltage. This paper analyzes the causes of electromagnetic oscillation overvoltage and induced overvoltage when the transformer coil is subjected to the impact voltage, calculates and simulates the wave process of the power transformer, uses the wave process calculation software to design the transformer insulation structure, and finally points out that the wave process calculation is an important basis for the longitudinal insulation design of transformers.