<p>In this study, a set of self-designed 20 L dyeing equipment was employed to investigate the application of color matching kettles with different structural designs in dyeing polyethylene terephthalate (PET) under supercritical carbon dioxide (scCO₂) treatment. The dyeing effects of horizontal and vertical color matching kettle were examined when the ratios of disperse blue 291 (DB 291) were 0.05% to 0.80%. In light of the findings and consideration of the relative merits and disadvantages of different placements for color matching kettles, it is preliminarily believed that the vertical configuration of the color matching kettle is a suitable choice for practical production. In addition, the vertical color matching kettle was further explored to determine the optimal holding time under different dye ratios. Moreover, treatment at (363.15 ± 2) K and (23 ± 1) MPa did not disrupt the molecular structure of DB 291, thus ensuring the stability of the dyeing process.</p>