Abstract: In order to objectively analyze and evaluate the usability of flue-cured tobacco chemical constituents in the Guangdong tobacco-growing area, an evaluation system of chemical composition of flue-cured tobacco was constructed by adopting fuzzy mathematics, multiple statistics and others with C3F flue-cured tobacco samples collected from 8 major producing counties in the Guangdong tobacco-growing area from 2013 to 2017. The time and regional characteristics of chemical components in the leaves of flue-cured tobacco were analyzed, and the usability of tobacco chemical components was evaluated. The results showed that in the recent 5 years, the contents of total sugar (25.09%), reducing sugar (21.83%), chloride ion (0.25%), the sugar nicotine ratio (8.52) and nitrogen nicotine ratio (0.69) in middle leaves were relatively low. The chemical composition usability of tobacco leaves of "moderate" and above accounted for 85.00%. There were significant differences in total nicotine, total nitrogen, potassium ion content, sugar nicotine ratio and nitrogen nicotine ratio in tobacco leaves between years and the regions, but there was no significant difference in the usability of chemical components in tobacco leaves between producing areas. According to chemical composition, there are three types of flue-cured tobacco in the Guangdong tobacco-growing area, each of which is relatively concentrated in the same ecological area respectively.