This paper presents a transmission line model (TLM) for the GSM base station lightning transient analysis, which is based on the use of the well-known ATP-EMTP software package. Direct lightning strike to the GSM base station tower is modelled with the Heidler’s type of surge current source. The earthing grid and the GSM base station’s tower structure by circular cross section conductors are approximated. In numerical model, conductors are subdivided into segments (1D finite elements) and Clark’s model with distributed parameters is used. Because of limitations of ATP-EMTP software package, the leakage resistance of buried segments is modelled as lumped parameter. Analytical expressions for distributed and lumped segment parameters are derived using the average potential method.