Abstract: To study the fracture process of FRP reinforced concrete beam before instability, a cohesive zone model for interfacial debonding due to mid-span crack was established based on the theory of concrete fracture mechanics and the bond-slip law of non-linear FRP-concrete interface. The formulas of interfacial shear stress, FRP tensile stress and fracture toughness before instability of FRP reinforced concrete beams were deduced by analytical method, providing an effective method for analyzing FRP-concrete interface debonding. Three-point bending experiments of FRP reinforced concrete beams with four different initial crack-depth ratios (0.2, 0.3, 0.4 and 0.5) under dynamic load were carried out. The experimental results show that, the crack initiation load and crack resistance load of FRP reinforced concrete beams decrease with the increase of initial crack-depth ratio. When the initial crack-depth ratio is 0.4, the crack initiation of specimens is the latest. The crack initiation toughness and the crack resistance toughness do not change with the change of the initial crack-depth ratio, which is consistent with the observations of other references and verifies the correctness of the analytical solution for fracture toughness.