Abstract: The influence of goaf on the stability of high-voltage transmission line towers has become a key problem in engineering construction. Based on the geological and hydrogeological conditions of a 500kv high-voltage transmission line over goaf in the southwest China, The paper explored the distribution of goaf, determined the height of the collapse fault zone and the depth of the impact of the building load, Besides, it makes analysis and evaluation on the stability of the tower foundation; And it also calculated the residual deformation of goaf, and analyzed the line security. The results show that: the impact depth of the load will not be transmitted to the collapse fault zone of N6 tower, the tower foundation is stable, residual deformation has a slight effect on the tower，high voltage transmission line operation is safe.