An investigation into the effect of surface roughness on corona discharge intensity of long-term operating conductors is presented. The electric field distortion level was found to increase linearly with surface average roughness Ra. At the corona inception voltages, the ionization intensity ξ in the ionization zone was calculated, it would increase exponentially with the raise of Ra. As a result, the corona discharge intensity of long-term operating conductors was stronger, and the corona inception voltages were lower than those of the new conductors. The deviation of radio noise and audible noise was found to increase linearly with the raise of Ra.