Changes of various chemical components during aging, inherent quality evaluation system and continuous-flow analyses of conventional components in tobacco were studied in this thesis. The results are as follows:1. Every score of inherent quality evaluating indexes of tobacco with different planting areas and grades increased differently during the aging process, reached optimal value after aging for 18 months and gradually decreased over that aging period. The contents of total sugar, reducing sugar, total nitrogen, total alkali, amino acid, protein, starch, total volatile alkali, nitrogenous compounds, linoleic acid, palmic acid, linolenic acid, polyacid and pH value in tobacco decreased all through the aging process, and these changes gradually leveled off after 18 months. But the sugar and alkali weight ratio , the Schmuck's value and the contents of lower aliphatic acids, myristic acid, oleic acid, stearic acid, higher aliphatic acids, inorganic compounds and aromatic alcohol gradually increased during the aging process. The contents of the determined ketones increased during the aging process except for solanone.2. Every factor affecting tobacco inherent qualities were analyzed with system theories, the system structures and state behaviors of inherent quality evaluation were determined, and the system structure model of the tobacco inherent quality evaluation was also established. The inherent quality evaluation system, Z={(P(i), Rz)}, is the associating aggregate of every chemical component in tobacco; and P( i )={ p(1 ), p( 2 )……p( n )}, is the sub-aggregate of every chemical component.3. Using correlation analysis and regression analysis, conclusions could be elicited that sugar and alkali weight ratio and Schmuck's value are positively correlatiive with every puff evaluation index, but nitrogen and alkali weight ratio is somewhat negatively correlative with aroma quality, aroma quantity, offensive taste, strength and total puff evaluation score. Malic acid positively correlates with aroma quality and aroma quantity, while malonic acid negatively correlates with them. Myristic acid positively correlates with inherent quality indexes and linoleic acid, negatively. Linolenic acid is extremely negatively correlative with after-taste of puff