Abstract: In order to investigate the structural changes of tobacco during thermal processing, ATR-FTIR spectroscopy was used to monitor the heating process of tobacco, and the effects of temperature on the structure and components of tobacco were studied by means of perturbation-correlation moving window analysis. The results showed that: 1) The physical and chemical changes of tobacco during heating process mainly included: removal of adsorbed water molecules, volatilization of small molecular organic acids, dissociation of hydrogen bond structure in tobacco, melting of small molecular organic compounds and oxidation of hydroxyl groups. 2) The transition temperature corresponding to the spectral intensity changes of O—H and C—H groups was 154 ℃ and the transition interval was 148-162 ℃; while the transition temperature of spectral intensity changes of C=O groups was 156 ℃ and the transition interval was 150-162 ℃, indicating the occurrence of violent physical or chemical processes, such as oxidation and removal of small molecules, in these temperature intervals.