Long-distance, large-capacity UHV transmission lines have increasingly become a key part of the construction of my country’s UHV power grid. However, with the increase of voltage levels, the electromagnetic interference of UHV transmission line towers to neighboring radio stations has become more and more serious, resulting in It is inevitable to study the secondary radiation suppression method of UHV transmission line towers. Therefore, based on the mechanism of suppressing the maximum value of secondary radiation, this paper proposes a secondary radiation suppression method for UHV trans- mission line towers in the mid-wave frequency band, and develops a secondary radiation suppression device based on the principle of this method. The final result shows that when the secondary radiation suppression device is not installed, the electromagnetic interference received by the measurement point is 0.4dB; after the secondary radiation suppression device is installed, the electromagnetic interference received by the measure-ment point is reduced to 0.1dB.