| Epoxy-bonding a carbon-fiber composite plate to the tension face of concrete beam is an effective technique for repair and retrofit of concrete beams. In the first part of this paper, based on the fracture mechanics and the theory of beam, a theoretic model is proposed to analyze the shear stress in the adhesive between carbon-fiber composite and concrete. And then the closure-form solution for the shear stress distribution is drawn. At different value of the main parameters that govern the shear stress distribution such as CFP adhesive length, CFP thickness and the anti-shear modulus of adhesive, the distribution of shear stress is studied. This leads to an easy understanding of the influence of some geometrical and material parameters. The following principles are proved: Increasing CFP adhesive length will release the concentrating of shear stress near the cutoff point, this will lead to the increment of loading-bear capacity of concrete beams; Increasing the thickness of CFP will improve the transition of load from concrete beam to CFP, this is useful to exert the potential of CFP; In creasing the anti-shear modulus of adhesive will result enhance the concentrating of shear stress, this is harmful to the effect of CFP reinforced concrete beams.The main body of this paper focuses on experimental research of CFP reinforced concrete beams. The experiment highlights the effect of CFP length and the adhesive mode of CFP on the loading-bear capacity of CFP reinforced beams. From the results, it is obvious that when the CFP adhesive length increases, the loading-bear capacity increase too. When the CFP length is 10mm, the loading-bear capacity is 1.81-2.27 times as much as the value of non-reinforced beam; And when the CFP length increase to 200mm and 350mm, the loading-bear capacity increase to 3.35-3.97 times and 3.61-5.76 times as much as the value of non-reinforced beam. By contrast, the effect of improving the adhesive mode of CFP, that is to say, epoxy-bonding double carbon-fiber composite plates or epoxy-bonding U shape CFP anchorage is less notable. The loading-bear capacity of double CFP reinforced concrete beams is 8.5-11.3 percent higher than that of the single CFP reinforced concrete beams; the loading-bear capacity of epoxy-boding U shape CFP anchorage reinforced beams is 4.7-18 percent higher than that of the single CFP reinforced beams. Additionally, the experiment also studies the effect of crack depth on reinforced concrete beams. The result indicates: whatever adhesive mode is taken, it is true that the deeper the crack is, the more notable the effect is. What's more, this paper studied the failure mode of CFP reinforced concrete beams and the process of the crack's extending based on the phenomenon that were observed in the experiment and the ultimate failure form of samples. There are three kind of failure mode of the CFP reinforced concrete beams: shear failure mode I, shear failure mode II and debonding failure mode. The cause of shear failure mode I is that the shear stress peak exceed the shear strength of concrete, so the shear crack formed and extended along the direction of angle of 45o to the longitude of the concrete beam. The extending of this shear crack leads to failure of samples. This mode appears in the case that the CFP length is 200mm. if during the shear crack's extending it run through the original crack which is locate on the middle of the beam, so from then on the original crack will extend quickly and this will lead to the failure of the samples. This is the failure mode II. It always appears when the CFP length is 100mm. The debonding failure mode is that during the loading process, the original crack extends and leads to the debonding of the CFP and the failure of the samples. This mode appears in the case that the CFP is 350mm.
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