Abstract: In order to study the effects of threshing and redrying process on the releases of the major phenolic compounds including hydroquinone, catechol, resorcinol, phenol, paracresol and orthocresol in mainstream cigarette smoke, three different grades of tobacco leaves, namely, B3F, C3F, and X2F, were tested. The results showed that: (1) seven different phenolic compounds in mainstream cigarette smoke release amounts were significantly related to the grades and positions, the order was: B3F＞C3F＞X2F; (2) for B3F and X2F tobacco leaf, the order of effect of threshing and redrying process on the release of phenolic compounds was: tobacco redrying＞one time moistening＞two time moistening, for C3F tobacco leaf, the order was: one time moistening＞tobacco redrying＞two time moistening.