Abstract: In order to clarify the different contents of chemical components in cigar tobacco leaves harvested at different time and their roles in tobacco leaf grading, the chemical components in cigar tobacco leaves of cv. Brazil 3 were analyzed. The results showed that the correlation of the mass fractions of total alkaloid and potassium in the leaves with harvest time were extremely significant with the correlation coefficients of 0.872** and -0.915** respectively. Cluster analysis was carried out by taking the contents of total alkaloids and potassium as cluster factors. When the number of clusters was 5, the cluster centroids between groups of cigar tobacco leaves of cv. Brazil 3 harvested at different time were uniform and their distances were obvious with the similarity up to 95.1%, which indicated that the contents of total alkaloids and potassium could reflect the quality differences among the leaves harvested at different time and could be used as important reference indexes in leaf grading. The result of cluster grouping showed that the appearance quality index, body, of cigar tobacco leaves closely related to the contents of total alkaloids and potassium in tobacco leaves.