Abstract: At present, the traditional insulated pole electroscope is used for electrical inspection in high-voltage transmission lines. However, when it is used in ultra-high voltage (UHV) transmission lines, the length of its insulated rod is large, and there are disadvantages such as large working intensity, inconvenience, and hazardous operation. In this study, an electroluminescent inorganic material was made to be used for inspection mark. The material was placed around the wire, so that it glowed during the electric fielddriven movement of electrons to promote carrier recombination, through which the charged situation could be determined. Therefore, the electrification of the line can be judged through the material luminescent properties, making it very convenient to be used for inspection mark. In this study, GaN materials were investigated. Based on the GaN, InGaN, and other materials, the contact layer, substrate layer, material layer and other structures were made by methods such as sol-gel method and gas phase epitaxy. Then the inspection mark was prepared. The light-emitting layer was a nanorod array with a multi-quantum hydrazine structure. The electrical and optical properties of the inspection mark were tested, and the relevant characteristic curve was obtained. Through a simulation of the Ansoft-maxwell finite element software, the electric field distribution of the inspection mark and surrounding transmission lines were analyzed. Through experiments, the electromagnetic environment needed for electroluminescence was tested in the high-voltage test hall of Wuhan University. Finally, the inspection mark was tested in a working environment simulated in the Feng-huang ultra-high voltage test site. The research shows that the low-field electroluminescent inspection mark has the advantages of low power consumption and obvious luminescence. When it is in an area where the electric field strength is above 1.2×10⁶V·m^-1, the light can be excited and the injected current is about 1.1 mA. Simulation and experimental analysis show that the electric field strength around the UHV transmission lines meets the requirements of the light-emitting indication of an electroscope. Meanwhile, the space stray current and capacitance effect of the material provide the injection current. The inspection mark indicates the charged state through the light-emitting properties. Its installation can be within a distance of 13 cm from the UHV conductor axis, and it has good weather resistance. Meanwhile, it avoids problems such as electromagnetic interference and poor reliability that occur in electroscope equipment with complex circuits.