The Linfen kiln complex, one of the most representative of Shanxi kilns, is famous for its oil spotted glazed ware production. In this work, micro-Raman spectroscopy was applied to analyze the nature of the rusty oil spot pattern of a bowl fragment from Linfen kilns. Crystals of polygonal shape found in the spots at the glaze surface and around bubbles in the cross-section of the glaze were identified as hematite. Their distribution in the glaze suggests that nucleation seeds and small crystals are carried toward the surface by the rise of bubbles during the heating step of the firing. Raman spectra combined with energy-dispersive spectrometry (EDS) measurements also suggest that Fe ions in hematite crystals are partially substituted, causing the variation of band position and full width at half maximum (FWHM) of the spectra. Dendritic ε-Fe2O3 was identified in brown areas of the black glaze, as well as pseudobrookite crystals of tens of microns in the cross-section of the glaze. The degree of the glaze polymerization (A500/A1000) was calculated at 1.85, indicating a firing temperature lower than 1300°C, consistent with the archaeological data.