To compensate for the existing norms lack in technology applications of harbor concrete structures strengthened by CFRP and solve the spotty problem of components with different corrosive grades strengthened with CFRP,powered by NaCl solution to simulate the corrosive marine environment,RC beams were accelerated corroded to different grades,and the comparison tests of corrosion beams flexural strengthened with CFRP were carried out.By analyzing capacity loss and reinforcement effects of the beams with different corrosion degrees,the effects of corrosion grades on RC beams flexural strengthened with CFRP were studied in this paper and the corrosion threshold between bonded directly with CFRP and bonded after chiseling off in the strengthening of RC Beams were discussed.The results showed that,within a certain corrosion threshold,the corrosion grades had significant effects on the flexural strengthening of corrosion RC beams bonded with CFRP,and bonded directly with CFRP can effectively reduce the width of the main cracks,decrease the cracking time,and improve the capacity and overall stiffness of corrosion beams.However,such strengthening effects became more and more insignificant with the increase of corrosion grade.As the RC beams corroded to a certain level,the directly bonded with CFRP was no more suitable for the strengthening,and the corrosion crack width 1 mm and corrosion section loss rate 15% as the threshold between directly bonded with CFRP and bonded after Chiseling off for the strengthening were determined.