Debonding failure is commonly observed in FRP-strengthened RC beams. It can be classified into two types: plate end debonding and intermediate crack induced debonding. Intermediate crack induced debonding is the main failure mode in FRP-strengthened RC beams.There is no specialized experiment study on this failure mode. To investigate intermediate crack induced debonding failure of FRP-strengthened reinforced concrete beams, 9 CFRP-strengthened reinforced concrete beams were tested. Based on the investigation of the strain in the FRP laminates, the width of the main crack and tributary crack, as well as the phenomena of the test beams, the whole debonding process can be separated into three stages: initial debonding stage, stable debonding stage, and the final debonding failure. The fundamental reason of intermediate crack indued debonding are the opening-up of intermediate crack and the flexural deformation induced high interfacial shear stress and peeling stress. When the principal tension stress acting on the concrete substrate exceeded the tension stress of concrete, the CFRP laminate would debond from the concrete substrate.