Abstract: To clarify the relationships between sugar coordination (total sugar and reducing sugar) and sensory quality of flue-cured tobacco, experiments were set up in eight ecological areas with different leaf quality gradients. The correlations of the reducing sugar and total sugar ratio and difference (RRT and DRT) with sensory quality were analyzed, and the contribution rates of RRT, DRT and other chemical components to sensory quality were analyzed based on the random forest model. The results showed that there were significant differences between RRT and DRT in tobacco leaves from the different ecological areas. RRT was higher and DRT was lower in the leaves from central Henan and southwestern Sichuan, but the opposite trend was found in eastern Yunnan and western Fujian. RRT and DRT were significantly correlated with leaf appearance quality indexes such as color, maturity, softness and oiliness, and smoking quality indexes such as aroma quantity, concentration, aroma quality and total sensory score. Significant differences were found in the contribution rates of RRT and DRT to the appearance and smoking quality of flue-cured tobacco in different ecological areas. In western Henan and central Henan, RRT and DRT had higher contribution rates to all appearance quality indexes, followed by eastern Yunnan, western Fujian, southern Hunan and southwestern Sichuan. In western Henan and southwestern Sichuan, RRT and DRT had the highest contribution rates to aroma quality, aroma quantity and total score of smoking quality, and the contribution rate of RRT to the total smoking quality score was 58% and 40%, respectively. In western Fujian and southern Hunan, RRT and DRT had the highest contribution rates to several smoking quality indexes. Therefore, RRT and DRT can be used as important indexes to evaluate the coordination of tobacco chemical composition based on their high contribution rates to the sensory quality of flue-cured tobacco in different ecological areas.