Abstract: Micron-sized metal dust is inevitably produced in DC gas-insulated switchgear (GIS), which can lead to insulation faults such as flashover. The use of particle traps is an important method to mitigate metal dust. In this paper, an observation platform to observe the trapping behavior of metal dust was built, and the capture mechanism of particle trap to metal dust was analyzed from the aspects of multi-physical field force and collision energy dissipation, based on the observation of the trapping behavior of dust with different sizes. The results showed that, after the initial movement of dust, a dust-free zone was formed between the dust and the particle trap. The 240 mesh dust was distributed in a ladder shape in the trap, and the 1 000 mesh dust was concentrated at the edge of the trap and in the trap slot near the dust pile. The smaller the particle size is, the more significant the influence of the van der Waals force and gas resistance on dust movement is. The Van der Waals force increases the lifting voltage of dust, and the gas resistance reduces the velocity of dust. With the decrease of dust particle size, the extreme values of the lifting voltage of dust and the velocity when it moves to the bottom of the shell will appear. The capture effect of particle trap to metal dust depends on the trap electric field shielding effect and the trap dust collision energy dissipation within the trap. When the size of the metal dust particles is large, the collision recovery coefficient is high. This leads to more frequent collisions between the dust particles and the trap, making it easier for the dust to be captured. When the size of metal dust is small, the collision recovery coefficient is approximately 0, and the metal dust will be adsorbed onto the trap surface and can not escape after moving to the trap.