The invention discloses a method for producing an electrolyte for aluminium and recovering carbon through recycle of aluminum electrolysis carbon residue. The method comprises steps of pretreatment, flotation separation, preparation and post-treatment, and specifically comprises: crushing electrolysis waste old carbon material, removing scrap iron through magnetic separation, performing separation on the electrolysis waste old carbon material subjected to pretreatment to obtain a bottom flow product and a foam product; performing filtering, carbon-removing and crushing on the separated bottom-flow product to obtain a target electrolyte for aluminium; performing pressing filtration and drying on the separated foam product to obtain a target carbon powder; and recovering flue gas and wastewater generated during preparation, and discharging when flue gas and wastewater reach the standards. According to the method, waste materials badly needing processing are taken as the raw material, various resources are completely recycled, waste gas is completely recovered and subjected to purification processing, also the produced electrolyte for aluminium is low in water content and less in harmful impurities, and is an ideal raw material for aluminium electrolysis production, and the carbon powder obtained through flotation can be used as a dye during production of aluminium electrolysis bottom pastes or bottom carbon blocks or metallurgy production.