Fibre-reinforced plastic (FRP) materials have been thought as new innovative materials for concrete rehabilitation and retrofit, the bonding of FRP plate to reinforced concrete (RC) structure has been a popular method for strengthening deficient RC structure. This paper presents a finite element investigation into interfacial stresses in an FRP plate partially bonded concrete beam. The finite element results show that both normal stress and shear stress at the a middle to adhesive section are influenced by the material and geometry parameters and the length of debonding FRP plate of the beam