The steel coped beams are commonly seen in steel structures since slotting and coping are inevitable for the fitting of steel beams. The steel coped beams with slender web, however, are prone to local web buckling, which results in decreased load carrying capacity and catastrophic failure modes. This paper is intended to investigate the feasibility of reinforcing single-coped beam with carbon fiber reinforced polymer (CFRP) plate. Totally five single-coped steel beams with or without CFRP plate reinforcement were tested. The failure processes and influences of different parameters were discussed and compared. It was found that the application of CFRP plate is effective to prohibit the development of buckling line. Thus, the load carrying capacity of CFRP reinforced single-coped beam could be three times higher than its control group. A novel finite element (FE) model was proposed and verified with experimental results. Based on the FE model, the failure mechanisms of CFRP reinforced single-coped beam were investigated. The parameter analysis was also conducted to acquire the optimal size of the CFRP plate considering its reinforcement effects. Based on both experimental and simulational results, the simplified design method of CFRP reinforced single-coped beam was also proposed.