Abstract: Based on a normal steel reinforcement configuration, fifteen concrete beams have been cast and tested. In order to strengthen the beams, CFRP (Carbon Fiber Reinforced Plastic) laminates is inserted and epoxy resin is filled after opening different dimensional grooves along the axial tensile area of the concrete–protection. The failure mode, crack moment and ultimate moment of the beams are studied and compared with those of the beams strengthened with EBR (External Bonded Reinforcing) CFRP. The crack moment and ultimate moment of the beams strengthened with NSM CFRP, the transformation and crack development of the test beams with the strengthening amount and groove width are analyzed. The results indicate that the load-bearing capacity of the beams strengthened with NSM CFRP increases from 11.2% to 41.7% comparing with the beams which are not strengthened, and from 15.5% to 22.7% comparing with the beams strengthened with EBR CFRP.