The present invention refers to the field of flue gas purification, which discloses a method and apparatus for capturing carbon dioxide and producing sulfuric acid by sodium bisulfate; using a three-format electrodialysis apparatus to convert the desulfurized by-product NaHSO4 into H2SO4 while capturing CO2 in the flue gas in the cathode chamber. Under the action of electric field drive and ion exchange membrane, HSO4− enters the anode chamber to generate H2SO4 and is concentrated, and Na+ enters the cathode chamber to generate NaOH; the flue gas containing CO2 to be treated is introduced from the cathode chamber and absorbed by NaOH. The invention provides a simple, green, and economic proceeding method to capture the carbon dioxide in the flue gas during the comprehensive utilization of sodium bisulfate solution, which is of better environmental benefits and improvement of the flue gas treatment technology and reducing the pressure of desulfurization gypsum treatment.