On the basis of the crack characteristics of aging RC beam bridges, the cross-section of RC simple beams with different pre-cracking levels were strengthened by the externally bonded FRP（EB-FRP）and the FRP-bolt hybrid bonding（HB-FRP）respectively to check the strengthening characteristics of HB-FRP. The flexural test with symmetrical loading on two points was conducted to study the mechanical behavior and failure mode of pre-crack beams strengthened with EB-FRP and HB-FRP. The influence of pre-cracking level on the FRP initial debonding load and FRP utilization ratio was assessed respectively. The test results show that the flexural capacity of pre-cracking beam strengthened with HB-FRP can be improved by 30%~44% compared with the one with EB-FRP. The failure mode has been changed from FRP brittleness debonding of beam strengthened with EB-FRP to obvious ductility failure of beam strengthened with HB-FRP. Furthermore, the crack distribution of RC beam has obvious influence on the FRP initial debonding load, the FRP utilization ratio and the failure mode of strengthened pre-crack beams.