A strengthening system for RC columns with adhesive-bonded vertical carbon fiber reinforced polymer （CFRP） plates was proposed. The strengthening system consisted of prefabricated vertical CFRP plates adhesively bonded to the column surface and a concrete jacket preventing the CFRP plates from debonding. To investigate the effect of adhesive-bonded CFRP plates on flexural behavior， five full-scale rectangular RC columns were tested under lateral cyclic loading. Experimental results showed that the cracking load of CFRP-strengthened columns was significantly improved compared to that of the reference column. The ultimate load-carrying capacities of the CFRP-strengthened columns were improved by 15.1% and 17.4%， respectively. The flexural capacity， and stiffness were improved by adhesively bonded vertical CFRP plates. However， no significant improvement in load-carrying capacity and stiffness of columns was observed for different amounts of CFRP plates. The ductility factor of the strengthened columns decreased by 16.2% and 35.1%， respectively. Since the limitation of column-foundation joint capacity， the strength of CFRP plates was not fully developed， and the CFRP strain at column failure was 24% of the ultimate strain. In addition， the proposed strengthening system was applied in a hospital strengthening project. A follow-up study showed that the flexural capacity of strengthened columns was significantly improved. The proposed strengthening system has been recognized by the civil engineering industry.