Geological disasters are likely to cause movement and deformation of the transmission tower foundation, resulting in failure or even damage to the tower structure, seriously affecting the safe and stable operation of the transmission line. Aiming at the damage of a 500 kV tower caused by geological disasters, a method based on the fourth strength theory to judge the failure of the rod is proposed, which can accurately determine the failure position and failure degree of the rod. The ANSYS software was used to establish the refined finite element model of the tower, and the constraints of the tower foundation under various geological disasters were applied. The stress of the tower was analyzed based on the failure criterion. The results show that when the settlement of the tower base reaches 29 mm, the cross-section of the tower leg is buckling and unstable. When the settlement reaches 76 mm, the main material of the tower is ineffective; the settlement and inclination of the tower are the most serious damage to the tower. Side slip has less effect on the tower. According to the characteristics of tower failure, the suggestions for tower structure reinforcement and disaster monitoring and prevention are put forward. Combined with the actual project, it provides a certain guiding role for the stability analysis and treatment of the tower under geological disasters.