The theoretically accurate prediction for cracks in concrete structures is difficult to realize. Applications of the optical frequency domain reflectometry (OFDR) technique in the identification and monitoring of cracks of concrete structures are studied by using the model test of concrete beams. Test results show that the OFDR technique can realize the warning of 0.002 mm micro-crack in concrete structures. The crack position can be located with a spatial resolution of 1 cm. The development process of cracks can also be monitored. Compared with other distributed monitoring techniques, the OFDR technique is more accurate in crack location and development monitoring and has a broad application prospect.