Abstract: In order to investigate the change of polyphenols and other compounds, and relative enzyme activity in tobacco leaf during tobacco processing,the changes of polyphenols,starch,total sugar,reducing sugar,total nicontine,total nitrogen and the activities of polyphenol oxidase(PPO) and total amylases in tobacco before and after 6 key process steps were tested and analyzed.The results showed that:the contents of polyphenols,starch,total sugar,total nicotine and total nitrogen decreased through the 6 key process steps;and activities of PPO and amylase reduced persistently after first conditioning and lamina storing;reducing sugar decreased in all the key process steps except for lamina storing.