Abstract: In order to study the effect of the construction of Erqi Yangtze river bridge on electric field of thunderstorm, the BEM （Boundary Element） method, based on the IES electromagnetic field simulation software, which is used to simulate and analyze the change of the electric field before and after the construction. The influence of the height of different negative charge centers on the main tower and the ground electric field strength is further analyzed. The electric field variation of the main tower is simulated with the lightning leader step by step, which is assumed eight different locations of lightning leader. The spatial distribution of the electric field is given, the characteristics of the electric field variation are analyzed, and then the possibility of lightning strike point is analyzed. The results show that after the bridge is built, the electric field intensity on the top of the bridge tower increases obviously; The height of the negative charge area in the thundercloud decreases gradually, and the electric field intensity on the ground increases gradually; The relative position of the lightning leader and the main tower of the bridge determines the most likely lightning strike point.

Key words: Erqi Yangtze river bridge, electric field of thunderstorm, IES simulation