The suspension span frame is connected with the transmission tower through the temporary beams on both sides of the transmission line crossing span and the hanging flexible sealing device is used to protect the safety of the crossing objects below. The impact load of the conductor is transmitted to the transmission tower through the suspension span frame under the condition of conductor breaking accident. At present, the condition of conductor breaking accident is not considered in the design of the spanning tower, in view of this, influence of suspension span frame on transmission tower under accident condition and reinforcement measures are analyzed through the 5E1-SZKK tower. A simulation method of conductor impact based on nonlinear dynamics of flexible body is proposed. The simulation results show that the maximum value of the impact load on the tower is 107.5 kN and the loading direction of each point is complex. The 790-820 and 900-952 diagonal members of the tower exceed the limits by 0.438 and 0.473 respectively. After the reinforcement of 5E1-SZKK tower by increasing the section technology, the utilization ratio of the members meets the requirements.