Abstract: In order to optimize the chemical suitability evaluation indexes of flue-cured tobacco, 412 samples of different qualities from 7 ecological regions were collected in two consecutive years. The correlations between free amino acid components in tobacco leaves and their sensory quality and appearance quality indexes were systematically analyzed. The results showed that:1) The contents and compositions of the free amino acids in flue-cured tobacco leaves from the different ecological regions were different, among which the largest difference of total free amino acid content exceeded 100% among the leaves from 7 regions. 2) Different components of the free amino acids showed different correlations with tobacco sensory quality. The contents of most amino acids (except for proline) and their ratios to the total free amino acid content were negatively correlated with the quality indexes, such as aroma quality, taste comfortableness, color purity and oil. The ratio of proline content to the total free amino acid content was positively related with the tobacco sensory quality. The relationship between the free amino acid components and sensory quality of tobacco leaves was consistent among planting areas and stable in the two years. The content of basic amino acid or its ratio to total free amino acid content, and the ratio of proline to total free amino acid content could reflect the sensory quality of tobacco leaves, which could be used for evaluating the chemical suitability of cured tobacco leaves.