In order to achieve damage identification of steel-concrete composite beams based on distributed long-gauge fiber bragg grating (FBG) sensors, model tests and finite element analysis of composite beams under impact loads were conducted. The damage assessment index βn constructed from the dynamic macro-strain spectral amplitude was used to identify damage of steel girder section and stud connections, respectively. The research results show that when long-gauge FBG sensors are continuously arranged along the longitudinal direction on the bottom surface of steel girder, the macro-strain of the sensors in the damaged area increases significantly. When the evaluation index βn>0, it can be determined that cross-sectional damage has occurred within the range of the sensor, and this index is more sensitive to the crack height on the web of the steel girder than the expansion width on the bottom flange. For stud damage, long-gauge sensors can be arranged in pairs symmetrically on both the upper and lower surfaces of the interface in concrete slab and steel girder, and the measured macro-strain time history can be subtracted to obtain the slip macro-strain time history. Then, based on the evaluation index βn obtained from the amplitude of the slip macro-strain spectrum, and using the two-stage identification method, the location of damaged stud can be identified effectively. Overall, reasonable arrangement of the distributed long-gauge sensors can realize damage identification of different components in steel-concrete composite beams, especially the connectors which are concealed in the concrete slab.