Provided is a method for separating zinc and iron in smoke of an electric-arc furnace. Starch is adopted as a reducing agent, hydrothermal reduction leaching is carried out on the smoke of the electric-arc furnace in sodium hydroxide solutions with additives, the zinc enters lixivium, the iron is transformed into magnetic iron oxide to enter the lixivium, and the zinc and the iron can be effectively separated; CO2 is piped into the lixivium with the zinc to adjust the pH value of the solutions, and basic zinc carbonate is produced; leaching residues produce the magnetic iron oxide and tailings through magnetic separating. According to the method, the zinc and the iron are effectively separated, and meanwhile magnetic separation and recycling of subsequent iron are facilitated. The CO2 is selected to adjust the pH value of the solutions for zinc depositing, and the advantages of being environmentally friendly and low in cost are achieved. The corrosivity of an alkaline aqueous solution system on equipment is greatly reduced, meanwhile, hydrothermal reaction temperature is controlled between 150 DEG C to 300 DEG C, and compared with a pyrogenic treatment process, energy consumption is greatly reduced.