The electric field of transmission lines is calculated by the charge simulation method. Considering the influence of transmission tower, the electric field of transmission lines needs to be calculated in three-dimensional space. In this scenario, if the transmission lines are segmented and the charge is calculated directly, the charge will gather at both ends of the transmission lines because the two ends of the transmission lines are suspended, which is inconsistent with the actual situation. In addition, the transmission lines will be affected by the transmission tower, which will lead to the uneven distribution of the charge. When using the charge simulation method to calculate the charge of the transmission lines, it needs a finer segment, and the amount of calculation will increase rapidly. In order to solve the electric field of the high voltage AC transmission line in this scenario and improve the calculation efficiency, this paper proposes a simplified method to reduce the number of unknowns and the amount of calculation and to eliminate the end effect of transmission lines. The transmisstion lines change and the electric field around the tower are calculated by solving the equation matrix. The correctness of this method is verified by a case. This method can be used to calculate the electric field around the transmission tower of multi-level high voltage AC transmission lines.