The invention relates to a device and a method for processing active carbon containing heavy metals and fine dust. The device comprises a feeding device, a plasma furnace, a waste heat recovery device, a sharp quenching device, a desulphurization and dust removal tower and a condensing device, wherein the desulphurization and dust removal tower comprises a seriflux storage section, a flue gas stabilizing section, a filtering section and a defogger; the filtering section of the desulphurization and dust removal tower comprises a plurality of filtering units; and the inlet of the filtering unitis in the shape of a circular cylinder, an outlet is in the shape of a horn, the diameter phi 1 is 80 to 500mm, the diameter phi 2 is 200 to 900 mm, the divergence angle alpha is 4 to 9 degrees, the length L1 is 100 to 450 mm, and the length L2 is 600 to 2500 mm. The invention adopts the remolded desulphurization and dust removal tower, and is characterized by depriving the fine dust and heavy metals in the desulphurization at the same time, wherein the removal rate of dust with the size of 1 to 5 mum can reach more than 90%; and the removal rate of divalent mercury can reach more than 85%.