Abstract: Multi-scale particles in engineering site may be produced in the operation of AC/DC gas insulated switchgear/gas insulated transmission lines, in which micron-nano dust is dispersed by the coupling field. With the characteristics of small size, strong physical and chemical activity and high concealment, micron-nano dust greatly threatens the safety of equipment insulation. In this paper, the research progress at home and abroad is reviewed, including dispersion concentration detection and spatial distribution visualization detection technology of micron-nano dust. And the evaluation methods of insulation risk degree of transmission equipment is summarized. On this basis, the key problems and technical means that need to be broken through in micron-nano dust detection and risk assessment are proposed. High-precision dispersion concentration detection technology of micron-nano dust is the basis for studying and analyzing the evolution characteristics and dispersion mechanism of dust scattering. The visual detection technology of spatial distribution provides technical supports for realizing the tracing of micron-nano dust and exploring the characteristics of spatiotemporal dynamic behavior. A quantitative evaluation system for dust hazard assessment can be established by the micron-nano dust characteristic information obtained by dispersion concentration detection and visual detection technology. The exploration of visual detection technology for micron-nano dust characteristic information also provides ideas for the study of micron-nano dust discharge morphology detection and discharge mechanism. Finally, the technical approaches to solve the visual detection of micron-nano dust are summarized, which provides a reference for studying the dispersion evolution mechanism and spatial distribution characteristics of GIS/GIL micron-nano dust.