The safety of the transmission tower located in the mining subsidence is susceptible to earth’s surface deformation, while the deformation of the tower foundation has the characteristics of from nonexistence to pass into existence, from small to large, from single to composite. Therefore, it is of great engineering significance to study the safety evolution law of transmission towers in the deformation process of tower foundation. Taking a 500kV transmission tower located in the mining subsidence as the research object, internal force and deformation law of transmission tower are calculated based on the finite element method under three meteorological conditions respectively: 90° high wind, 45° high wind and ice coating, during the single and double foundation composite deformation process. The results show that during the single and double foundation composite deformation process, the maximum stress transfer path of the members is similar, and the safety of the tower is less reduced in the early stage of deformation, and the safety rate of the tower is accelerated in the middle and late stages. Under three meteorological conditions, the evolution law of the safety of the transmission tower in the deformation of the tower foundation is similar. It is reco mmended to carry out monitoring and reinforcement measures for the tower legs with the largest deformation and the first section of the transverse joints on the same side in the early stage of the deformation of the tower.