The transient behaviour of a transformer station grounding system subjected to a lightning strike is investigated using a field theory approach. When lightning strikes and transformer station, large currents generatd by stroke flow in the grounding system and dissipate in the soil, The electromagnetic fields generated by such high currents may cause damage to equipment and may be dangerous to the personnel in transformer station. A field theory method should be used to obtain an accurate representation of the transient behaviour of the lightning process in the transformer station grounding system. In this paper, the frequency domain response of a transformer station grounding system subjected to a lightning strike have been modelled. numerical results are presented graphical form.