Abstract: Buffer layer ablation defect is an important cause of high voltage cross-linked polyethylene (XLPE) cable failure. However, there is no effective detection method for this defect at the cable operation site. To improve the detection rate, detection speed, safety, and portability of the buffer layer ablation defect in XLPE cable, the relationship between characteristic gases (CH₄, C₂H₆, C₂H₄, C₂H₂, CO, and H₂) and the buffer layer ablation defect was studied, and detection technology for the characteristic gases of the buffer layer ablation defect in XLPE cable based on the Fourier transform infrared spectroscopy was proposed. A buffer layer ablation characteristic gas analyzer was developed. The performance of the method and device was verified by environmental monitor, mixed gas detection, and simulated ablative gas detection, respectively. Finally, the device was applied to the 220 kV XLPE cable fault site to verify the method's feasibility further. The results show that the temperature, humidity, and pressure measurements are accurate, with an error of less than 10%; the detection errors of the characteristic gas concentrations are less than 7%, and the detection period is less than 1 minute; the volume fractions of the characteristic gases are all positively correlated with the ablation time, which can characterize the ablation defect of the buffer layer. At the same time, the field application results further show that the method can be effectively used for detection of characteristic gases of on-site buffer layer ablation defects, which provides strong supports for the rapid diagnosis of buffer layer ablation defects.