Abstract: The usability index (CCUI value), which represents the quality of tobacco leaves on the basis of chemical components in tobacco leaves was calculated with fuzzy mathematics and principal component analysis method to comprehensively evaluate the usability of Qujing tobacco leaves on the basis of their chemical compositions, and the influences of chemical components on sensory quality were analyzed. The results showed that: 1)The contents of nicotine, potassium and chlorine, and the ratio of nitrogen to nicotine in Qujing tobacco leaves were moderate, while the contents of total sugar and reducing sugar, and the ratios of potassium to chlorine and sugar to nicotine were higher, the contents of total nitrogen and starch were slightly lower. 2)Chlorine content did not differ significantly between grades, total nitrogen content did not differ significantly between varieties and the ratio of nitrogen to nicotine did not differ significantly between varieties or growing areas. The other chemical components differed significantly or extremely significantly between grades, varieties or growing areas. The order of usability among grades was C3F> B2F> X2F, among varieties was K326> Hongda> Zhongyan 100> Yunyan 85> Yunyan 97> Yunyan 87> NC102> NC297, among growing areas was Shizong County> Luoping County> Qilin District> Luliang County> Xuanwei City> Zhanyi County> Huize County> Malong County. 3)The grey incidence analysis indicated that the chemical components in Qujing tobacco leaves mainly affected ash color, combustibility, impact and aroma quality in sensory evaluation.