Abstract: To research the characteristic of the lightning current distribution of a mobile communication base station tower stricken by a lightning, this paper proposes a novel circuit method and establishes a circuit model which describes a network system comprising the tower and its grounding network. We analyze the lightning current distribution and the impulse impedance characteristics of the tower. Simulation indicates that the lightning current distribution of the tower and the antenna cable shielding layer depends on tower structure and lightning position, while it is nearly immune to the earth resistivity. Furthermore, direct lightning on any position creates nearly identical leakage currents, which occurs on grounding conductors at symmetrical location of the grounding network. In addition, as the height of lightning point to the ground rises, integrated resistance and reactance of the "tow-er-grounding network" network increase a little, where, the changes of reactance are faster than that of the resistance. In all, results provide significant references to lightning protection design.