From the point of view of pure chemistry, it is generally believed that the changes in the process of alcoholization and fermentation of flue-cured tobacco leaves are mainly pure chemical changes (mainly oxidation reactions), and the effects of enzyme catalysis and microorganisms are secondary; According to the theory of microbial action, the initial cause of tobacco fermentation is the participation of microorganisms, which restrict the fermentation process and quality, and the later stage of fermentation is carried out under the action of inorganic catalysts. According to the concept of enzyme change, tobacco fermentation is a biochemical process involving its own enzymes, which is the result of retaining active enzymes after tobacco leaves are dried. Although the mechanism of tobacco aging and fermentation is still inconclusive, the problems that can be confirmed are as follows: the fermentation process is mainly an oxidation reaction, and the main feature of the fermentation process is to consume oxygen to varying degrees and release co2 and heat. Tobacco leaf fermentation is completely different from alcohol fermentation of other plants, and there is no connection between them. The changes of tobacco leaves in the process of alcoholization and fermentation are not the continuation of various physiological and biochemical changes in the process of modulation, but there are great differences between them.