Abstract: Neural oscillatory changes play a critical role in pain and analgesia research. Previous studies on pain-related neural oscillations have primarily utilized electroencephalogram (EEG) power spectral analysis, revealing a strong correlation between alpha (α) power and subjective pain perception. However, α power spectra are potentially influenced by baseline variations in the power spectrum. This study employs power spectral analysis and further applies a power spectral parameterization method, which decomposes the power spectrum into periodic and aperiodic components, to investigate EEG α power in 50 primiparous women undergoing severe pain during the first stage of labor before and after epidural analgesia. The results indicate no significant differences in α power between pre- and post-analgesia conditions. However, following power spectral parameterization, the non-periodic component of the EEG significantly decreased after analgesia, whereas the periodic component of α power showed a significant increase. This study not only validates the effectiveness and validity of the power spectral parameterization method in analgesia research but also uncovers the differential regulatory mechanism by which analgesia modulates the periodic and aperiodic components of α oscillations.