In order to reduce the power frequency grounding resistance, the communication base station grounding network should be bonded to the power tower grounding device to form a common grounding system. Firstly, the time domain simulation model of the common grounding system is established, and then the tower grounding union simulation model is constructed to analyze the lightning response characteristics of the tower shared with the grounding system. For the underground part, based on the numerical simulation results of the method of moments, the time domain equivalent circuit model is established by the vector fitting method, which can more accurately describe the broadband response characteristics of the common grounding system. In the frequency domain solution, a frequency sampling optimization method based on rational approximation is adopted, which can improve the calculation efficiency; for the ground part, the classical Hara multi-wave impedance tower model is adopted. The two situations of the communication room arranged root span or next to a tower are discussed respectively, the simulation results show that the maximum deviations of lightning transient overvoltages on the top and cross arm of the tower before and after communication and power grounding system sharing are small, and the tower sharing will not affect the lightning response characteristics of the tower.