The invention relates to a gas dust removal method used in the process of extracting metallic silicon by high temperature electric arc. In the invention, double-layer draining water jack furnace mantle is additionally arranged above a metallic silicon smelting furnace chamber; a vertical chimney is arranged above the furnace mantle; a honeycombing metallic pipeline is arranged in the chimney; onepart of the outer wall of the pipeline is in welding seal with the chimney; circulating cooling water is filled between the outer wall of the pipeline and the inner wall of the chimney; and high-temperature gas flows through the water cooling jack. By using the water cooling method, dust grains brought in a dust removal device by high-temperature gas flow are reduced, the collection purity of silicon dioxide is increased, the temperature of gas flow is lowered to protect a bag-type dust remover, and the service life of the bag is prolonged.