Steel structures are damaged for a variety of reasons including accidental loads, corrosion and reduced strength ‎which need to be repaired and improved. In this investigation, local corrosion was applied to the steel circular columns ‎and the effects of Carbon Fiber Reinforced Polymer (CFRP) for ‎strengthening has been studied. 19 specimens of steel ‎Circular Hollow Section (CHS) column ‎with the same height and damage dimensions under compressive load were ‎analyzed by ABAQUS software which six cases of them were performed experimentally. In laboratory cases, ‎progressive corrosion was used to create damage on the specimens. In order to improve the accuracy of the analysis, a ‎combined ‎method was used to study the post-buckling of the plastic zone. For this purpose, the ‎specimens were first ‎subjected to elastic buckling analysis and then Riks non-linear analysis ‎with global and local imperfections was ‎conducted. The results showed that the corrosion ‎reduces the bearing capacity and rigidity of the steel columns‏ ‏and ‎complete destruction of the corroded area reduced the load bearing capacity by 40% for the column with corrosion at ‎the middle and by 21% for the damage close to the base, which shows the former is more critical. Strengthening of ‎columns retrofitted with carbon fibers restored ultimate load reduction by 33% and have a positive effect on ‎controlling fractures and reducing stresses at the damaged area. ‎