Provided are a method for processing titanium extraction slag and a carbon extraction and dechlorination tailing. The method comprises the following steps that a titanium extraction slag raw material is ground to obtain a treated material with a particle size being 0.3˜120 μm and d90≤90 μm; a first solvent and a treated material are mixed with a liquid-solid ratio of (3.5˜4.5): 1 L/kg, and a first capturing agent and a first foaming agent are added for mixing and then subjected to a primary flotation to obtain a floating product and a sinking product; and a second solvent is added into the floating product to adjust the liquid-solid ratio to (4˜5): 1 L/kg, a second capturing agent and a second foaming agent are added for mixing and then subjected to a secondary flotation to obtain a foam product; the foam product is filtered and dried to obtain a refined carbon, and the sinking product is filtered and dried to obtain the carbon extraction and dechlorination tailing, wherein the d90≤90 μm means that more than 90% of the powder in the treated material has a particle size of less than 90 μm. The method has the advantages that carbon in the titanium-extracted slag can be recycled, chlorine is removed, and the carbon extraction and dechlorination tailing can be used as a building material raw material.