Abstract: Based on the field investigation methods, the damage severity and flood inundation area at the scene of a collapse accident for the No.170 tower on the 500 kV Shiyan-Xiangfan circuit in Gucheng County on 6 August 2012 were investigated and analyzed. Then the hydrological and meteorological conditions in the disaster period as well as the reservoirs, river channels and physical geography in the disaster area were investigated and arranged using data analysis methods. We calculated the extreme values of water level, discharge, precipitation and other factors, and simulated the flood path and the depth and context of flood inundation by a two-dimensional hydrodynamic model, to assess the cause of the tower collapse event. The results show that the tower collapse event induced by rainstorm is obviously characterized by the disaster chain effects. Due to the local heavy rainfall inducing mountain torrents and the middle and small river floods, both the inflow peak discharge of Tankou reservoir and the peak discharge of the Beihe River in Gucheng exceed the record for once in 100 years. The great impact of the flood damaged the trees, houses, bridges and other disaster bearing bodies on the flood path first, and then the debris evolved from the disaster bearing bodies and the flood combine together to become a new disaster causing factor, resulting in the tower collapse due to the collision of upstream flood and debris. The simulated flood inundation area in the upstream of Tankou reservoir where the tower 170 is located increases with time, which is basically consistent with the inundation area confirmed by the field investigation.