Abstract: The ±1 100 kV power line communication(PLC) noise filter can effectively filter conduction high-frequency interference noise, so as to avoid its interference on power line carrier communication signals of the power system. The PLC reactor is one of main devices of the noise filter, which is connected in series in the main circuit of noise filter. In order to determine the structure form and dimension of grading and shielding devices of ±1 100 kV PLC reactor, firstly, according to the preliminary design dimensions, the 50% switching impulse discharge tests and 3D electric field simulation theory calculation are carried out, the value of critical breakdown field strength of ±1 100 kV PLC reactor is obtained. Secondly, aimed at the parts where the surface field distortion of the grading and shielding devices are relatively serious, the external diameter and pipe diameter are studied and optimized, and the distribution of the surface field strength of the PLC reactor in the laboratory and in the actual operation environments are compared and analyzed. Finally, the switching impulse discharge test for real ±1 100 kV PLC reactor is carried out by using 250/2 500 μs standard switching impulse and 500/5 000 μs long-front switching impulse. The results show that the optimized grading and shielding devices of ±1 100 kV PLC reactors can meet the practical needs of the project, and provide technical support for the design of external insulation parameters of ±1 100 kV PLC reactors.