Abstract: The existence of metal particle swarm in DC GIS/GIL seriously threatens the insulation performance of the equipment, and the wire particles will undergo firefly. To clarify the firefly motion mechanism of the wire particle swarm, this paper proposes a firefly motion observation platform, and obtains the motion characteristics of the wire particle swarm. Furthermore, the charged motion model of particle swarm is established, and the dynamic simulation of wire particle swarm is realized. The results show that the onset voltage of the particle swarm is negatively correlated with the number of particles, and increases with the increase of particle diameter while decreases with the increase of particle length. The lifting voltage of the particle swarm decreases in the stacked state, but the onset voltage of the particle swarm is not affected by the initial states of the particles. Compared with the single particle, the changes of Coulomb force, space charge and field strength between particles make the wire particle swarm lead to a series of irregular suspension and random spanning motions exhibited by the wire particle swarm. The particle swarm significantly reduces the electrical strength of the equipment, and further evaluates the risk degree of the wire particle swarm motion behavior based on the air gap breakdown effect of the particles. The specific results show that for the wire particle swarm firefly, the risk of the ground electrode single particle firefly is the lowest, the risk of the high voltage electrode single particle firefly and the stationary particles firefly is higher, and the risk of particles flying around is the highest. This study provides a reference for the main insulation design of the equipment in terms of suppressing the movement of the particle swarm.