The carbon fiber has been widely applied in the building reinforcement because of its light weight, high strength, good viscosity, heat resistance, corrosion resistance, anti-fatigue, easy to be cutting and constructed, etc. Considering the FRP strengthened experimental data of large and full-scale concrete beam is relatively insufficient, in this paper, two strengthening methods, namely, near-surface-mounted and externally-bonded carbon fiber plate, are used for of contrastive experimental study of eight full-scale concrete beams, to analyze the influence of two strengthening methods on bearing capacity, deformation and failure mode of concrete beam, etc.The analysis results show that two strengthening methods can improve the mechanical behavior of concrete beam, its yield load and ultimate load, and delay the crack development.The externally-bonded strengthening method, however, has a high request for bonding technique, otherwise, the debonding and failure easily occur; while the near-surface-mounted strengthening method can effectively avoid the failure, and give full play to the high strength of carbon fiber plate, so this kind of strengthening method should be generalized and wildly applied.