Abstract: To investigate the quality changes of pipe tobacco during high-pressure and high-humidity fermentation, Kuiliu tobacco leaves from Sichuan were examined. The variations in color, routine chemical components, aroma components, pyrolysis products and sensory quality were systematically investigated using appearance, chemical and sensory analysis methods. The results showed that: 1) Color difference analysis showed that the color of the raw materials significantly darkened within 90 days of high-pressure and high-humidity fermentation, and the color difference value reached its maximum (7.98±0.31) on the 180^th day of fermentation (F6). The color remained relatively stable at the later stage of fermentation. 2) In the early fermentation stage, the contents(mass fractions) of reducing sugar and total sugar in the raw materials decreased notably, while the contents of potassium and chlorine increased in varying degrees. The contents of total alkaloids and total nitrogen exhibited a downward trend over fermentation time, with the sugar-to-alkaloid ratio decreasing from 0.40 before fermentation (F0) to 0.08-0.13 after fermentation. 3) The total content of aroma components in tobacco leaf samples showed an increasing trend followed by a decreasing trend over fermentation time, ranging from 851.27 to 2, 137.21 μg/g. The high-pressure and high-humidity fermentation process primarily promoted the accumulation and transformation of key aroma components, such as acids, esters and alcohols. 4) A total of 87 pyrolysis products were identified across all tobacco leaf samples, including acids (3), aldehydes and ketones (19), heterocycles (26), esters (7), phenols (13), olefins (12) and alcohols (7). The samples with total contents of pyrolysis components ranking from the highest to the lowest were those fermented for 360 d (F12), 180 d (F6), 270 d (F9), 90 d (F3) and the unfermented sample (F0). 5) Fermentation significantly improved the sensory quality of Kuiliu tobacco leaves. The samples fermented for 180 d (F6) exhibited good aroma quality with notable reduction in offensive odor and irritation.