High-voltage and ultra-high-voltage power transmission grids are exposed to natural environment all the year round, which often makes plastic and other non-metallic foreign bodies overlap on cables, towers, insulators and other power grid facilities. It will lead to poor insulation between high voltage power cables, which has become one of the major threats to the normal operation of power system. Laser, as a new light source, with its high energy, strong monochromaticity and good coherence, has a good application prospect in the removal of non-metallic foreign bodies such as plastic polymers. The use of laser to remove non-metallic foreign bodies winding transmission lines has the advantages of fast, efficient and safe, and has been widely used in the removal of foreign bodies in high voltage and ultra-high voltage power grids. Atmospheric environment will affect the actual use of laser, which can cause the attenuation of laser energy and seriously affect its effect of ablation. In order to accurately obtain the attenuation of laser propagation in rain and fog, the attenuation model of laser propagation in rain and fog is established, and the transmittance of laser in rain and fog is analyzed. An experimental platform for laser attenuation in rain and fog was set up in this article. When the rainfall intensity and transmission distance change, the ablation effect of polymer plastics on high voltage transmission lines with different laser power is studied experimentally. The results show that the effect of laser ablation is largely affected by rainfall intensity and transmission distance. When the rainfall is 40mm/h, the maximum distance of ablating polymer plastics with 100W laser power is 60m, and the maximum distance of ablating polymer plastics with 300W laser power is 120m. When the rainfall is 60mm/h, the maximum distance of ablating polymer plastics with 100W laser power is 30m, and the maximum distance of ablating polymer plastics with 300W laser power is 90m.