The underground goafs poses a major threat to the safe and stable operation of surface power facilities, reasonable detection of goaf can effectively reduce the possibility of accidents. The power towers used are mostly made of iron materials, which have high conductivity and high permeability. They are very easy to influence the electromagnetic detection signals. With the aid of the relevant simulation software, the model of a three-dimensional goaf under the power tower is constructed. The influence of the excitation region, injection current, excitation mode, tower volume and radius on the range of the tower is analyzed. The results show that the power tower will seriously influence the electromagnetic signals near it, and the influence is most prominent near the center of the tower, but the change of the exciting region and the injected current will not change the function range of the tower. When the electromagnetic survey is carried out in the goaf near the power tower, a relatively long range emission excitation signal should be adopted and the signals near the power are detected simultaneously or remove the detection data near the power tower, which can partly reduce the influence of the tower on the electromagnetic detection of the goaf.