Ablative defects in the buffer layer of high-voltage cables are important causes of power cable failures. Buffer layer ablation releases gases, and some components of these gases and their concentrations can characterize the degree of buffer layer ablation defects. Fourier transform infrared spectroscopy for buffer layer ablation gas analysis has the unique advantages of speed, sensitivity, and non-destructiveness. To address the challenges in the detection of gases from high-voltage cable buffer layer ablation, namely noise interference, baseline drift and cross-interference, a buffer layer ablation gas Fourier transform infrared spectroscopy analysis method is proposed. The proposed method is validated by standard concentration gas analysis and ablation characteristic gas analysis experiments, using CH₄, C₂H₆ and C₂H₄ as characteristic gases. The experimental results show that the three characteristic gas concentrations are related to the buffer layer ablation defects, and the proposed method can accurately analyze the concentration of the characteristic gases from infrared spectra, with relative errors of 8.90%, 17.60% and 4.32% for CH₄, C₂H₆ and C₂H₄ in mixed gas, and the detection period is less than 15 s. This method can provide critical technical support for rapid, high-precision diagnosis of buffer layer ablation defects in high-voltage cables.