Abstract: To investigate the effects of wet bulb temperature during the yellowing stage of curing process on the quality and metabolite transformation of tobacco leaves, middle leaves of Cuibi 1 (CB-1) were studied and the wet bulb temperatures for the early, middle and late yellowing stages were set as 37.0-37.5 ℃, 36.0-37.0 ℃, 36.0-37.0 ℃ (T1, low tempreture and humidity treatment), 37.5-38.0 ℃, 38.0-39.0 ℃, 38.0 ℃ (T2, middle tempreture and humidity treatment), and 38.0 ℃, 39.0-40.0 ℃, 36.0-37.0 ℃ (T3, high tempreture and humidity treatment). The chemical composition and sensary quality of the cured tobacco leaves were evaluated, and the differential metabolites between the three curing treatments at the yellowing and color-fixing stages were identified using non-targeted metabolomics techniques. The results showed that: 1) Compared with T1 and T3, T2 yielded the most favourable index values, including the contents of nicotine, total sugar, reducing sugar, chloride ions and sugar-alkali ratio, chlor-alkali ratio and potassium-chloride ratio. It also achieved the highest scores for sensory style and quality characteristics, with a more pronounced flavor style and superior freshness, sweetness and aroma quality, and the best overall sensory score. 2) Metabolomics analysis identified 4, 327 metabolites in CB-1 tobacco leaves across the three curing treatments. From the middle and later yellowing stage to the middle color-fixing stage, more than 2, 000 differential metabolites were identified among the three treatments. The greatest number of differential metabolites was observed at the later yellowing stage, indicating that wet bulb temperature at this stage was critical for the quality formation. Significant changes were observed in differenrtial metabolites including organic nitrogen compounds, carbohydrates, flavonoids, alkaloids, terpenes and lipids during the curing process. 3) Compared with T1 and T3, T2 exhibited more complete conversion of organic nitrogen compounds at the later color-fixing stage. Carbohydrate decomposition produced more sweet substances such as melibiose, catalpol, galacturonic acid, L-gulose and mannotriose, contributing to the fresh and sweet flavor style of tobacco leaves under T2 treatment. Under T2 treatment, the relative abundances of glabridin, betanin, aconine, and acetylvalerenolic acid were high, and the aroma style and characteristics were more distinctive. Furthermore, the relative abundances of reserpine, oripavine, baptifoline, ergotamine and α-narcotine at the later yellowing stage were relatively high under T2 treatment.