Abstract: In order to explore the change of grade quality under the new loose-leaf purchasing mode, 7700 bundles of C3F tobacco from 154 batches of grade quality supervision and inspection samples in 2018 industry/commerce handover, including samples from 12 prefecture (cities), 79 counties (cities, districts) in Yunnan, were studied. Principal component analysis was carried out among 7 factors influencing grade quality, including mixed low grades, mixed cany leaves, mixed variegated, mixed parts, mixed medium quality, mixed bottom part, and mixed low quality, from which 3 principal component factors were extracted. Based on the comprehensive scores of principal components, cluster analysis was performed using the 154 batches of tobacco leaves from different growing areas. The results showed that: (1) The grades C4F and X2F exhibited ralatively high proportion among mixed non-sampled grades; (2) The cumulative contribution rate reached 87.608% for the 3 extracted principal component factors, among which the contribution rate of the 1st principal component was 44.722%. Mixed low grades, mixed medium grades, mixed stalk positions, and mixed bottom leaves were the principal factors influencing the grade quality of C3F; (3) K-Means analysis clustered the 154 batches of C3F tobacco leaves from different growing areas into 3 categories. The 1st cluster included 14 batches of which grade quality was mainly influenced by mixed variegated leaves and mixed inferior grades. The 2nd cluster included 127 batches of which grade quality was mainly influenced by mixed low grades, mixed medium grades, mixed stalk positions, mixed bottom leaves, but less influenced by mixed cany and variegated leaves. The rest 13 batches formed the 3rd cluster of which grade quality was mainly influenced by mixed cany leaves. The results from the principal component analysis and the cluster analysis accordantly agreed with each other. (4) Together with the mixed non-sampled grades situation, under the new loose-leaf purchasing mode, the major problems of C3F grade quality were mixed low grades and mixed stalk positon.