Abstract: To investigate the quality changes of pipe tobacco raw materials during high-pressure and high-humidity fermentation, the alterations in color, conventional chemical components, aroma components, pyrolysis products, and sensory quality of the raw materials were systematically studied using appearance, chemical, and sensory analysis methods, with Kuiliu tobacco leaves from Sichuan as the research subject. The results showed that: 1) Color difference analysis results revealed that the raw material’s color significantly darkened within the 0-90 d of high-pressure and high-humidity fermentation, reaching the maximum color difference value (7.98±0.31) at the 180-day fermentation (F6), and remained relatively stable in the later stages of fermentation. 2) In the early fermentation stage, the mass fractions of reducing sugar and total sugar in the raw materials decreased notably, while the relative mass fractions of potassium and chlorine increased to varying degrees. The mass fractions of total alkaloids and total nitrogen exhibited a overall downward trend as fermentation time extended, with the sugar-to-alkaloid ratios decreasing from 0.40 in the unfermented tobacco leaves (F0) to a range of 0.08-0.13 after fermentation. 3) The total mass fractions of aroma components in tobacco leaf samples initially increased and then decreased with prolonged fermentation time, with an overall range of 851.27-2 137.21 μg/g. The high-pressure and high-humidity fermentation process primarily promoted the accumulation and conversion of key aroma components, such as acids, esters, and alcohols. 4) A total of 87 pyrolysis products were identified for all the tobacco leaf samples, including acids (3), aldehydes and ketones (19), heterocycles (26), esters (7), phenols (13), olefins (12), and alcohols (7). The samples corresponding to total mass fractions of pyrolysis components ranked from highest to lowest were as follows: fermentation for 360 d (F12), 180 d (F6), 270 d (F9), for 90 d (F3), and unfermented (F0). 5) The sensory quality of Kuiliu tobacco leaves significantly improved after fermentation, with fermentation for 180 d (F6) exhibiting superior aroma and a notable reduction in off-flavors and irritation.