Abstract: In order to investigate the substance basis and action mode of tobacco smoke bitterness, by referring to the bitter mechanism and bitter substance basis in food flavor science, the contents, bitterness thresholds and taste active values (TAVs) of 13 alkaloids in smoke of 51 tobacco samples were determined or calculated with taste active value method, a bitterness index model for tobacco smoke was established, the model was further verified with sensory evaluation. The results showed that: 1) The calibration curves of the 13 alkaloids displayed good linearity with the correlation coefficients (R²) above 0.99, the average recoveries (n=5) ranged from 79.51 to 94.80% with the relative standard deviations (RSD, n=5) ≤ 10%. The developed method was suitable for quantitative determination of smoke alkaloids. 2) Myosmine, anabasine and nicotine made major contribution to smoke bitterness with TAVs over 20, especially myosmine; the TAVs of cotinine, nornicotine, nicotyrine, indole, and pyridine ranged from 2 to 20; and the TAVs of 3-ethylpyridine, quinoline, isoquinoline, anatabine, and 2, 3'-bipyridine were less than 2. 3) The bitterness index model for tobacco smoke based on the TAVs of the 13 alkaloids agreed pretty well with the results of sensory evaluation.