Abstract: Gas insulated transmission line(GIL) is inevitably contaminated by metal particles during production, transportation, installation, and operation, which affects the charge accumulation on the insulator surface and seriously reduces the insulation level of GIL. In this paper, based on the considerations of physical processes such as charge carrier generation, recombination, and migration on the gas-side, the effects of metallic particles and their micro-discharges are additionally taken into account, thus a time-varying 3-D numerical model of charge accumulations at the gas-solid interface of DC GIL with gas-side charge injection in dominance is developed. Meanwhile, numerical calculations of charge accumulation in the GIL geometrical model with metal particles attached to the center conductor are performed. The simulation results indicate that the presence of metallic particles distorts the surrounding electric field distribution and alters the surface charge distribution on the insulator. Under ideal conditions, the charge at the gas-solid interface of the insulator mainly exhibits a halo-shaped distribution. When metallic particles are attached to the central conductor, they accelerate the charge accumulation process on the insulator surface and promote the appearance of bipolar discrete charge spots. Additionally, the average charge density in the insulator region directly below the metallic particles is approximately 10.4% lower compared to that in the absence of metallic particles. Furthermore, a comparative analysis of the normal electric field characteristics on the insulator surface reveals that the presence of metallic particles causes an uneven distribution of the normal electric field on insulator surface.