Premature debonding between CFRP and concrete commonly occurs in RC beams strengthened with CFRP sheets. U-wrap anchorages installed at the ends of CFRP sheets or along the entire beams are currently well accepted for preventing the debonding failure in engineering practice. Three schemes of CFRP strengthening beams without U-wraps, with U-wraps at CFRP ends and along the entire beam are numerically studied. The loading capacities and deflections of the beams, bond-slips in the interfaces and strains of CFRP sheets in the three cases are compared under different loading levels. The result shows that the strength and stiffness of the strengthened beams are effectively improved with the clamping of U-wraps. After the yield of steel reinforcement, U-wrap anchorages along entire beam are more effective for preventing the debonding failure than those at CFRP ends and lead to the uneven strains of CFRP sheets as well At the ultimate state，CFRP can rupture locally at the places of high strain concentrations leading to decrease in the loading capacity compared to the beam anchored at two ends of CFRP.