With the rapid development of urban construction and the buildings in residential and commercial areas are more and more dense, substations are also getting closer to residential and commercial areas which leads to noise pollution caused by the substation becoming more and more serious. Theoretical analysis shows that the transmission line surface to increase the insulation material can effectively reduce the outer electric field strength of the wire, thereby reducing corona noise. When the outer layer of the wire has coating material, the temperature of the outer layer of the wire is higher than that without coating material, and for the same coating material when the load capacity is certain, the coating material thickness increases, the temperature of the outer layer of the wire also increases. In order to analyze the impact of the coating layer used in the corona noise reduction process on the surface field strength and thermal effect of transmission lines, this paper establishes a finite element simulation model to calculate the changes in the electrical properties and thermal effect of the wire surface at different thicknesses of insulation materials at 1000 kV voltage level, which can effectively guide the design of corona noise reduction.