This work is aimed at answering the question that whether the realkalisation as a rehabilitation method is effective on the corroded reinforced concrete structure or not. To this aim, the behaviour in a sodium carbonated solution whose concentration is 0.5 mol/L of reinforcing bars from an reinforced concrete structure that failed through carbonation after 70 years of service life is examined. The results show the electrochemical reaction on the rebar is closely related with the surface state of reinforcing bar electrode. During the electrochemical realkalisation treatment, the reduction of ferric oxide or ferrous oxide formed on the surface of reinforcing bar will occur in company with the producing of H2; The realkalisation treatment not only resumes the alkalescence of the carbonated concrete , but also rehabilitates the corroded reinforcing bar by reducing the rust to iron. The electrochemical realkalisation treatment is a rehabilitation method and has a repairing effect on some extent of corroded reinforcing bar.