Abstract: To determine the optimal harvest maturity for upper tobacco leaves in Panzhihua tobacco-growing area, a field experiment was conducted using Yunyan 87 as the test material. Four maturity treatments were established: under-ripe (M1), ripe (M2), mature (M3), and over-ripe (M4). The effects of different maturity levels on the routine chemical components, plastid pigments, appearance quality, and sensory quality of flue-cured tobacco leaves were systematically studied. The results showed that with increasing maturity, the contents of total sugar, reducing sugar, and total nitrogen gradually decreased, while the nicotine content increased continuously. The sugar-to-nicotine ratio and nitrogen-to-nicotine ratio decreased significantly, with the M3 treatment showing the best harmony of chemical components. The contents of chlorophyll a, chlorophyll b, and carotenoids all showed a significant decreasing trend. The appearance quality was optimal in the M3 treatment, followed by M2. Sensory quality increased initially and then decreased; the M2 treatment scored highest in the distinctness of flue-cured tobacco's pure-sweet aroma style, aroma quality, and aroma quantity, while the M3 treatment performed better in offensive odor, irritancy, and aftertaste. Based on the analytic hierarchy process and fuzzy comprehensive evaluation, the overall quality ranking of the treatments was M3 > M2 > M4 > M1. Considering the industrial usability of upper tobacco leaves, it was recommended that the harvest standard for upper leaves in the Panzhihua tobacco-growing area should be when the main and lateral veins turned white and bright, the leaf surface appeared yellow with slight green, the leaf tip began to dry up, there were many ripe spots, and the SPAD value was controlled between 21 and 25.

Key words: upper tobacco leaves, harvest maturity, chemical components, sensory quality, Panzhihua tobacco-growing area