Abstract: To clarify the regulatory pattern and underlying mechanism by which altitude influences the formation of quality and sweet-fragrant style in flue-cured tobacco from Liangshan. Flue-cured tobacco grown across altitudes of 1300~3000 m in Liangshan was analyzed through a multi-dimensional approach, including appearance quality, sensory quality, routine chemical components, plastid pigments, polyphenols, organic acids, amino acids, carotenoid degradation products, and phenylalanine-derived metabolites. Altitude had little effect on appearance quality, but exerted significant regulation on sensory quality and chemical traits. Altitude showed a downward-opening quadratic relationship with sensory quality, sugar-to-nicotine ratio, chlorogenic acid, and rutin, while an upward-opening quadratic relationship with nicotine, chlorophyll b, citric acid, and proline. With increasing altitude, phenylalanine and its metabolites increased continuously, whereas carotenoid degradation products first increased and then declined. Tobacco grown at 1 900~2 100 m exhibited a prominent sweet-fragrant style and superior sensory performance, coupled with a balanced sugar-nicotine ratio, and enrichment of aroma compounds such as polyphenols, carotenoid degradation derivatives, and phenylalanine metabolites. Meanwhile, contents of chlorophyll, organic acids, and total amino acids were relatively low, making this altitude range optimal for forming high-quality sweet-fragrant flue-cured tobacco. Planting flue-cured tobacco at elevations of 1 900~2 100 m can effectively improve the sensory quality of Liangshan tobacco and enhance its sweet-fragrant style.