Abstract: Gas insulated switchgear(GIS) is an indispensable physical support for the construction of new energy power system.Statistical analyses on ultra/ultra-high voltage discharge faults in ten years show that the discharge of metal particles and dusts accounts for more than 60%, the existing ultra-high frequency, ultrasonic sensing and other technical means can be used to achieve better online monitoring for large-size particles with sub-millimeter and above; however, micron-nano dusts are unable to be effectively characterized by the existing technology due to high randomness and, hidden and inevitable existence, thus it is very likely to be hidden in the back of the "safety killer". Therefore, in accordance with the difficulty in detecting micron-nano dust and the complexity of the mechanism, a micron-nano dust adsorption experimental platform suitable for observation and suitable for the actual operation of GIS is constructed, and it is found that the adsorption state of micron-nano dust in the electric field mainly consists of agglomerative adsorption along the insulator interface and diffusive adsorption along the direction of the ground electrode, and the key factors influencing the behavior of the movement include the initial position of the micron-nano dust, the quality, the material, and the applied voltage; it is further clarified that micron-nano dust may be the hidden safety killer behind. The special physical phenomena in the adsorption process are further clarified. Agglomerative adsorption will occur on the surface of the epoxy resin insulator to form a micron-nano dust speckle, meanwhile, with the increase of voltage, the micro-nano dust speckle will "explode" to form an annular dust halo, and the contour of the halo will be deepened, etc., which is different from that of the starting adsorption, and such special physical phenomena are considered to induce the flashover along the face of the insulator. This kind of special physical phenomenon is a necessary condition for inducing flashover along the surface. Finally, the physical mechanism of flashover along the surface triggered by micron-nano dust is revealed, and the localized short- circuit area and violent electric field distortion constituted by dust speckle are the important predisposing factors of micron-nano dust induced flashover along the surface, reducing the breakdown voltage up to 71%. In this paper, the research on the dynamic characteristics of micro-nano dust adsorption can provide a theoretical basis and technical support for improving the safe operation level of AC/DC GIS insulation.