Abstract: In order to determine the appropriate harvest maturity of dark sun-cured tobacco, the changes of main physiological indexes and chemical components during the curing process of sun-cured tobacco, and the differences of tobacco quality after sun-cured tobacco were studied with varieties Piaohe 1 and Piaohe 2. The results showed that there were significant differences in pigment content, amylase activity and main chemical components in tobacco leaves with different maturity. During the drying process, the moisture, pigment, amylase activity and the content of main chemical components of tobacco leaves with different maturity were different. With the increase of ripeness, the rate of dehydration increased during the air drying process, chlorophyll degradation was more complete, and the green color of leaves faded faster. With appropriately improved maturity, high amylase activity is maintained in tobacco leaves at the early stage of drying, which is conducive to degradation of starch and improvement of sugar content, while decreasing the total nitrogen and coordinating the chemical composition of tobacco leaves. In conclusion, the sensory quality of tobacco leaves of variety Piaohe 1 was better in M2 and M3, which means that the most suitable maturation is reached when 60%-70% of leaf surface turns yellow. After curing, the best sensory quality of tobacco leaves was M2, which means that the most suitable maturation is reached when 50%-60% of leaf surface turns yellow.