Abstract: For RC beams strengthened with bottom bonded CFRP sheets, debonding failure may occur before the CFRP rupture strength is reached. It is believed that the debonding failure is controlled by the bond stresses. Based on experimental research of four RC beams strengthened with bottom bonded CFRP sheets, a finite element method is used to analyze the bond stresses in the interface using MSC.Marc program. By separating the local bond stresses from the total bond shear stresses, the anchorage bond stresses along the extensional bond length are obtained, and the bond stress distribution is investigated. The concepts of "anchorage bond stress"and "effective anchorage bond length"are introduced, and a simplified distribution of anchorage bond stresses is proposed for determining the debonding capacity of the strengthened RC beam with bottom bonded CFRP sheets.