In order to master the dynamic response characteristics of transmission tower in mountainous area, taking the T-shaped transmission tower of 800kV UHV transmission line in mountainous area as the object, the finite element model of transmission tower rolling stone impact is established by using nonlinear explicit dynamic analysis software. The rod deformation, stress and time history change in the impact area of transmission tower are studied. The effects of rolling stone impact position, velocity, angle and mass on the impact response of transmission tower are analysed. The calculation formula of peak impact force of rolling stone of transmission tower is given and compared. The results show that the rolling stone impact force of transmission tower presents a triangular pulse shape, with short duration and large impact force; The deformation of auxiliary materials in the impact area of transmission tower is large, and the stress of its rod is the most unfavourable. During the impact, the stress level of the tower rod reaches the peak value instantaneously, then oscillates and decays rapidly, and gradually tends to be stable; After the impact of rolling stone, the tower pole will undergo plastic deformation, and the residual axial stress level of the tower pole is greater than the residual shear stress; When the impact position of the rolling stone is 1/6 to 1/8 tower height, the peak impact force of the rolling stone and the residual axial stress of the rod are relatively large. When the impact angle is 0 °, the impact response of transmission tower is the most severe. The impact velocity and rolling stone diameter have great influence on the impact response of transmission tower; The peak value fitting formula of impact force can be used to estimate the impact force of rolling stone of transmission tower.