The quality of cigarette mainly depends on the flue gas which composed the chemical composition.Study deeply to the chemical composition was very important to control the quality of cigarette.In order to evaluating the pyrolysis fingerprint in research and quality control of tobacco leaf and finding out the chemical different of tobacco leaf after burning, we applied pyrolysis-gas chromatography / mass spectrometry (Py-GC/MS) and chemometrics method to analyze flue-cured tobaccoI Were identified 87 compounds.PLS-DA analysis showed the classification of three kinds of tobacco leaves, and we found some related cracking compounds of the different samples.