Corrosion behaviour of rebars in concrete subjected to chloride ions and carbon dioxide rich atmospheres was investigated. In order to evaluate the corrosion characteristic, the corrosion behaviour of rebars in concrete in the presence of simultaneous contamination by chlorides and carbon dioxide were contrasted with that of the concrete contaminated with a single factor. Results indicate that compared with the concrete contaminated with single factor, the rebar corroded area and corrosion grade are higher in concrete exposed simultaneously to carbon dioxide and chlorides. However, with the increase of mole ratio of n(NO-2)/n(Cl-), the rebar corroded area and corrosion grade in concrete gradually decrease, and the rebar corroded area has dropped from 620% to 18% preserved in the experimental condition when n(NO-2)/n(Cl-) is 12.