Abstract: In “Technical Specifications for Strengthening Concrete Structures with Carbon Fiber Reinforced Polymer Laminate”, the overlap length of CFRP (carbon fiber reinforced polymer) is required to be 100mm at least. To examine the rationality of this requirement, based on the classical elasticity theory and elastic –plastic property of adhesive, a simplified formula to calculate the effective bond length of FRP single lap bond (SLB) is presented. Twelve groups of FRP SLB specimens were made by hand, and they were tested under static loading. The shear stress distribution in the overlap zone was measured, which leads to the derivation of the effective bond length of FRP SLB. The test results indicate that the maximum shear stress occurs at the ends of the overlap zone for any overlap length; and the effective bond length is estimated to be between 75 mm and 100 mm in Carbon specimens and between 100 mm and 125 mm in Glass specimens. The computed results using the presented formula were in agreement with experimental ones. This study confirms the requirement in “Technical Specification for Strengthening Concrete Structures with Carbon Fiber Reinforced Polymer Laminate”.