The fiber Bragg grating (FBG) wavelength shift in an FBG strain sensor which is caused by expansive rebar corrosion products will be detected and monitored by an FBG interrogator. Based on this principle,a new type of FBG corrosion sensor is proposed in this paper,which consists of an FBG corrosion measurement sensor, an FBG temperature compensation sensor,and a customized rebar which has a pair of radial grooves,a pair of axial grooves,and a through-hole located between the two axial grooves.The FB G corrosion measurement sensor is designed to measure the expansion strain caused by rebar corrosion,and the F BG temperature compensation sensor is designed to eliminate the cross-sensitivity of FBG corrosion measurem ent sensor.The customized rebar with radial epoxy fixing grooves is designed to install the FBG corrosion measur ement sensor on its surface and the sensitivity enhanced FBG temperature compensation sensor in the through-hol e which is finally connected with optical cable in axial grooves.The corrosion rate is derived by the wavele ngth shift of FBG corrosion sensor in this paper,so the rebar corrosion can be monitored and assessed by the FBG wavel ength shift.The FBG corrosion sensor is embedded in cement mortar and subsequently casted in concrete.The per formance of the FBG corrosion sensor is studied in an accelerated electrochemical corrosion test.Ex perimental results show that the new type of FBG corrosion sensor has relatively large measurement r ange of corrosion rate.The FBG corrosion sensor is suitable for monitoring slightly and moderately corroded reb ars,thus the FBG corrosion sensor can be employed to monitor the rebars in reinforced concrete structures,such as buildings,bridges and tunnels.