Ultrasonic guided waves use highfrequency signals in the detection of small cracks in rails, which will lead to significant signal attenuation and reduced detection sensitivity for small cracks. It is difficult to identify small cracks. In order to improve the recognition of defect signals, this paper uses barker code as the encoding method, and use BPSK-like as a decoding method, which is used in the signal processing of guided wave detection of small cracks in rails. The artificial crack with a depth of 6 mm and a width of 0.5 mm on the rail bottom will be verified through experiments. In order to measure the effect of the algorithm, the original transceiver guided wave signal without any signal processing and the guided wave signal processed by the barker code-matched filter codec are used respectively. Compare with the experimental method. The results show that the guided wave signal processed by the barker code-like BPSK codec has an obvious enhancement effect on the identification of small cracks at the bottom of the rail, and the effect is better than the other two methods, which can be used for the detection of small cracks in the guided rail in the future. provide support.