The invention discloses a process for producing sulfuric acid by adopting waste plaster and carbon dioxide and a film coupling reactor for implementing the process, wherein the process for producing sulfuric acid mainly comprises the following steps: sending the waste plaster, alkali-like compound materials and carbonate solution into a decomposition reactor to perform decomposition reaction so as to produce sulphate and calcium carbonate; sending the sulfate liquor to the film coupling reactor to perform the film coupling reaction, sulfate radical negative ions combine with Hions under the action of an electric field and the film to form sulfuric acid, and positive ions combine with HOions to form alkali sent to a dioxide carbon absorption unit; and absorbing carbonate formed by the carbon dioxide to return the decomposition reactor. The film coupling reactor comprises at least one reaction unit groove which includes an anode chamber and a cathode chamber that are formed by a negative film, a positive film and an anode and a cathode arranged correspondingly, and a feed liquid chamber, wherein the anode chamber is provided with a sulfuric acid solution discharging outlet and a water adding inlet, the cathode chamber is provided with an aqueous alkali discharging outlet and a water adding inlet, and the feed liquid chamber is provided with a feed liquid adding inlet.