Abstract: Propanediol isophthalate polyester (polyester) was prepared by esterification and polymerization reactions using isophthalic acid and 1,2-propanediol as raw materials, and its microstructure was determined using Fourier transform infrared spectrometer, nuclear magnetic resonance spectrometer, and mass spectrometer. Polyester mentioned above was filled into a quartz capillary tube to prepare a capillary chromatographic column, whose separation performance for phenolic isomers in industrial coking phenol and high-purity 3,5-xylenol was investigated. Meanwhile, thermal stability of the self-made capillary chromatographic column was evaluated using a capacity factor curve. It was shown that the softening point of the synthesized polyester was 85℃, and the polymerization degree was about 7. When using the self-made capillary chromatographic column to detect industrial coking phenol, except for 2,4-xylenol and 2,5-xylenol, the resolutions of 9 components including phenol, 2,6-xylenol, o-cresol, m-cresol, p-cresol, p-ethylphenol, m-ethylphenol, 3,5-xylenol, and 3,4-xylenol were greater than 1.500, with RSDs (n=6) of the peak areas of the 9 components less than 6.0%, and the theoretical plate numbers for 3,5-xylenol reached 2 662 m⁻¹. When detecting high-purity 3,5-xylenol, the tailing of 3,5-xylenol did not affect the separation of nearby impurities such as m-ethylphenol and 3,4-xylenol, with the average resolution between 3,5-xylenol and m-ethylphenol of 3.917, and the average resolution between 3,5-xylenol and 3,4-xylenol of 10.026, and RSD (n=6) of the peak area of 3,5-xylenol was less than 1.0%. The capacity factor curve of the self-made capillary chromatographic column was drawn, and the highest operating temperature reached 225 ℃. After continuous using for 7 d at the highest operating temperature, there was no significant change in the capacity factor.