Aiming at the problems such as low echo signal-to-noise ratio, high sidelobes, and wide main lobes, an ultrasonic guided wave detection method based on Nonlinear Frequency Modulation （NLFM）-Barker coding excitation is proposed. Firstly, Barker code is chosen as the base encoding, which is then combined with sinusoidal signals, line frequency modulation (LFM) signals, and NLFM signals, respectively. Secondly, the time-domain, frequency-domain, and pulse compression characteristics of the three composite coded signals are analyzed through simulations. The simulation results show that after weighted matching filtering, the NLFM-Barker pulse compression signal has the narrowest main lobe width, which is 9.23 μs at -6 dB. Finally, to further verify the effectiveness of the proposed composite coding excitation, defects are simulated by attaching mass blocks of different sizes to a 2 000 mm long CHN60 rail. The experimental results show that when the rail is intact, the main lobe width of the NLFM-Barker signal is reduced by 5.9%, and the peak-sidelobe level (PSL) is decreased by 2.161 4 dB compared to the traditional Sin-Barker signal. When defects are present in the rail web and NLFM-Barker coded excitation is applied, the energy variation of the received ultrasonic guided wave signal becomes more distinct across different defect sizes. To sum up, this study provides a reliable and effective solution for rail web defect detection and quantitative analysis.