CFRP (Carbon Fiber Reinforced Plastics) sheet has been used for the retrofitting of a number of existing concrete buildings and structures because of its excellent properties (high strength, lightness and high durability). To be an effective retrofitting system, however, bond effectiveness between CFRP sheet and concrete should be verified, and understanding of the peeling mechanism is especially important. This study employed both the experimental and the analytical methods to quantify the maximum bond stress τ_y and the effective bond length l_u, where the bond stress distributes. Here the interface is modeled as an interphase of 1 mm thickness, that is, a composite which consists of epoxy resin and concrete. The values of τ_y and l_u are finally proposed, and they are 4.56MPa and 45.2mm, respectively.