Abstract: In order to investigate the contribution of important basic aroma components in mainstream cigarette smoke to cigarette style characteristics, the activity thresholds of 25 important basic aroma components (pyrazines and pyridines) were obtained from their functional thresholds. The evaluation was conducted by sensory evaluation of functional thresholds for tobacco flavors and their releases in mainstream cigarette smoke as determined by GC/MS. The activity threshold data of 25 basic components were analyzed to pinpoint the important basic components in cigarette smoke demonstrating characteristic cigarette styles. The results showed that:1) The functional thresholds of the 25 basic components ranged from 1.00×10^-13 to 2.74×10^-5 μg·cig^-1; the levels of 2-methylpyridine, 2, 6-dimethylpyridine, 3-ethylpyridine and 2-vinylpyridine were lower, while those of 2-methylpyrazine and 2-acetylpyridine were higher. The maximum difference of functional threshold between these basic components reached eight orders of magnitude. 2) The total content of the 25 basic components in particulate matter of mainstream smoke was 11.130 μg·cig^-1, the contents of 3-vinylpyridine and 3-methylpyridine were higher (2.784 and 2.476 μg·cig^-1, and accounted for 25.0% and 22.2% of the total content, respectively). The contents of six basic components, such as 2, 3-dimethylpyrazine, were lower, and the sum of their contents only accounted for 4.0% of the total content. 3) The activity thresholds of the 25 basic components ranged from 1.20×10⁴ to 2.34×10¹², which was 6.51×10¹² in total. The activity thresholds of 3-ethylpyridine, 2-methylpyridine, 2, 6-dimethylpyridine and 2-vinylpyridine were up to 3.05×10¹¹-2.34×10¹², and the sum of which accounted for 99.9% of the total activity thresholds. These indicated that as key aroma components, the above four components played a decisive role in demonstrating the toasted aroma note of cigarette smoke.